Brake proportional valve

Im just replacing all brakes on my 4wd 1995 SC kzh106..i feel that back brakes may not be doing enough work..Yes they are adjusted correctly and i know that front brakes do most of the work.
The rear suspension has those heavy duty rear coil springs so the van is quite high.. The back of van has been gutted and is empty as i am turning into a campervan . Im wondering due to the height of the van, would this affect the proportional valve adjustment (combination valve/load sensing valve) ? Can proportional valve  be adjusted?
Edited :
after doing some research The height will affect the valve...I Might just adjust nut on valve 1 turn and go for a drive and test brakes.
Also the manuals i have seem to have a different type of load sensing valve to the one on my van.

I might have the same job in near future. Could you point me to the right direction of where one would get the manual regards brake proportional valve adjustments etc?

FRom what i read , the correct way is to load van with a weight, then plumb in pressure gauge to front brakes and one to rear brakes..and adjust valve as per manual...i havent got gauges so will adjust it manually and go for a drive on gravel and test it, adjust and retest etc etc,,,but will do this when i have the van loaded with camping gear and bed etc..when for 1000km run this weekend and front brakes are working their nuts of, so i will adjust the valve again, and will let u know what i find..
I also read  on google,, if van is raised by say 50mm, then the valve itself should be raised on brackets by 50mm..
I will try my way and see what happen, maybe i book it in on rollling road brake tester aswell.

Some will cringe the good old Kiwi way im doing it...lol

In the UK we have yearly road tests at a test station one part is a break test one wheel at at a time to check for brake balance if this is not correct front to back side to side etc it fails deamed un roadworthy .

Yep thanx i know..im english but been in NZ 27yrs....MOT or WOF stations usauly dont have rolling road?brake testers which amazes me..only the big guys like VTNZ check brakes properly like we are used to..smaller garages may just take it for a drive and see how it feels!!! bit scary really aye

If you get a IR sensing temperature gauge (some have a laser on to help the aim) you may be able to detect temperature which will give you an indication of how hard the brakes have been worked.
With alloys you could also feel with a finger too I suppose, as long as it's not too hot.

Good idea..i have a ir temp  at work...
Also my partner drove the van today whilst i was behind her,,she not used to auto gbox..drove down this really steep hill for about 3km in Drive!!!, she was on the brakes all the way down and she was going fast as she hadnt not put the van into 2nd, smoke bellowing from the front, and only just manged to stop at intersection!!!!!!!!!!!!!  had to give her a lecture on brake fade and explain engine braking...All though i think my brand new brake pads are rubbish..smoky , dusty dont stop when hot..Anyone know of the best heavy duty 4x4 type brake pads, brakes that stop when hot as we drive up and down mountains here in NZ and prefer to spend big bucks on Brake rather killing someone..thnks

Ah yes, interesting there was smoke from the front and not the back, maybe the back ones were not working so the fronts had too much work to do? Not sure if drums smoke much though.

I'd recommend a combination of new Toyota rotors and new Toyota pads, the combination of the materials matters. I'm not sure it matters a huge amount, but I feel it does matter a bit .

BTW if you stop when the discs are above 650C and leave the pads clamped on - the temperature and carbon from the pad forms an area of Iron Carbide.
This doesn't notice at first but eventually forms an island of carbide as the remainder of the disc wears and you get the 'warped discs' syndrome. I actually had this really badly on my discs when I first got my van so the first thing I did was new Toyota pads and discs and new brake fluid! Now after a heavy stop I knock it into N and use the handbrake only when at rest, on any vehicle.

So you may was well change them both now . Also new discs will bed in much faster. You do have to take the hub off but it's a hand-tight nut, just mark the spot on the nut to get it the same as before when reassembling.

The drums on the back were hot but not hot enough to burn me, they do work, but even tho brake is adjusted properly the handbrake has trouble holding...the brake linings are dry, no oil leaks , i think rear shoes need replacing for different shoes...Ive decided to go for the expensive Bendix heavy duty brakes which are on order from Australia.
Will look into new front discs/Rotors aswell..thnx

The big drums at the back should make quite good brakes, maybe the handbrake cable is jammed? I had that on a Peugeot, the stiff cable eventually got stuck on and the drum overheated and the shoes fell off!
Too hot to touch is about 50C, smoking brakes I'd estimate at 400-500C+ so there does seem to be a lazy rear brake problem IMO.

As noted the only issue for hydraulic action is the valve, and maybe sticky wheel cylinders, maybe take them off and rebuild them (clean up and re-assemble with plumbers silicone grease) to make sure they move well.

Not sure what else to suggest - maybe other people have comments about how good their rear brakes are. If you have a local brake testing place (MOT garages in the UK) could be worth a try to see how much braking effect is there.