Major setup problem...
 

OK guys here is the story.I drove a berg tracer for a while...had it setup quite well.
Limited the shocks 1" inside and 0.5" outside and used rubber bands to keep it low and always with longest wheelbase(set at 12.5").
After reading lots of posts here i decided to upgrade since everyone was pointing towards 4 shock setup...so i bought a VQ incision chassis, traxxas 5318 lower links and traxxas bigbore shocks with losi springs.
A common setup for this chassis and any berg axles.

THE problem comes when trying to climb edges.
The tracer chassis had good clearance even when pulled down with the rubber bands...so it always kept it's 12.5 wheelbase and could reach and catch edges where the VQ needed to be digged so it could stretch...BUT if grip is low, the front tires can't get any grip to stretch the chassis so you can't climb it, PLUS the upright position puts the weight of the front on the chassis which tends to extend the shocks thus shortening the wheelbase even more.................................WHAT DO WE DO???
Sell the VQ or is there a solution or tip...NEED HELP!

It's always gonna be a compromise one way or the other. The closer the upper links are to being parallel to the ground the less stretch you get when the shocks are compressed. To get a 12.5 wb at rest without rubber bands you would have to run the upper links 100% parallel to the ground and adjust the shocks to be fully extended at that point. The compromise would be when you dig and compress the shocks you would actually shrink the wb. The idea is to tweak the shock travel and links to get the most out of the wb without going over on the tech table. Depending on the setup I often use bumbstops on the chassis to pass tech so I can get a longer wb at rest. Hope that makes sense...

I never understood this theory for the upper links and their relation to wheelbase changes.

If i take it completely simple the only thing that affects the wheelbase changes are the lower links and how parallel these are with the ground...NOT the upper links.
Upper links only rotate the axle back and forth which doesn't affect the length.
But if the lower links are in an angle, then when the chassis is pressed down it wheel extend that difference from angled to parallel lowers.

How to uppers affect this?

And why do we need to have altered wheelbase ...isn't it better to have it set at 12.5 all the time??? where will this kind of setup lose compared to more traditional setups?

I believe only half your problem is in the setup of the rig, the other half is driving technique.

Try softer springs and oil on your shocks and lay them down a bit. I used to run the incision and I was running losi golds and 25wt oil on all 4 corners. Running that setup it would stretch on demand.

Now for the driving technique, I find that if I am going to need to stretch to reach a ledge that I have to start the dig way earlier than I originally tried to. You will have to play with it to get it right but if the rig gets too vertical then there isnt enough weight on the front end to get the tires to grab, if it is flatter then there is more weight pushing down and they will hook. Then you can toggle back to 4wd and then back to dig if you need to but try not to lose the length before the front grabs and pulls you up.

You maybe right about lower link effecting the wb more but an angle on the top link will roll the axle away from the chassis and lengthen the wb. A 12.5 wb all the time would be ideal but you would have to have the links parallel to the ground so when it was pushed down at tech it didn't go over the limit otherwise driving would be great. With the links like that I think the skid would be to low. Basically equal to the height of the lower link mount on the axle. Raising the belly would put an angle on the links and create an arc that would go past the limit. A droop setup would work but then you gotta deal with setting that up right.