More caster c hubs on older chassis? How much to add? Any 4WD buggy racers got some help?

[ThunderDragonCy 8430]

So I'm sitting here a bit bored at Taipei airport waiting for my flight home wondering idly about a new design project. I've noticed that top end 4WD racers have caster angle built into the c hubs to add to the kick up at the front of the buggy. Added to this as I've been filling my evenings this week whilst here on business, I found an article on Jamie Booths Manta Ray from 1991 and he says one of the biggest things he did was get some extra caster added to the custom c hubs he had made. 

I have a Thunder Dragon and a Terra Conqueror DF01 now, and I think fairly easily I could do caster c-hubs for them via Shapeways. I just have no idea how much to add. My DT03 has 25 deg, but I haven't seen that much on 4WD for some reason. Anyone got any ideas? Looks like both my buggies have something around 10 deg kick up, so should I be trying to add 5 deg? 10 deg? 15 deg? 

All help, hand waving, wild speculation greatly appreciated. 

Cheers!

[Saito2 7727]

I was curious as to why 2wd buggies had so much front kickup but not 4wd. I looked it up long ago and am fuzzy on the facts but I recall it had something to do with kickup effectively shortening the buggy's wheelbase on shock compression. Not a problem on 2wd, but on 4wd it does wonky things evidently due to all four wheels being driven. I imagine it doesn't do wonders for driveshaft angles either. But my vague memory may be best left as "wild speculation". I guess 4wd buggies could make up for the lack of kickup with caster built into the c-hubs (?). I remember Jamie Booth saying the early outings with the Egress did not go all that well. They were heating the lower arms and sticking a screwdriver through them and twisting them back to get some more caster angle if I recall. Of course part of that issue (the wandering, nervous nature of the Avante lineup) also deals with those cars' terrible scrub radius issues as well. I could be off on all this but its fodder for discussion.

[ThunderDragonCy 8430]

You're right about why they have less kick up. I am keen for someone who maybe has one of the TRF5XX buggies with castor blocks letting me know how much caster to add