Front end pancake and castor mod in one

[63inoz]

Just about to do a pancake on the 63 crossmember, read everything i can find on it, very confident, have all the tools etc.
While deciding whether to go 1.5 or 2" I realise that taking 2" out of the front still leaves plenty, but out of the back leaves it very thin in the centre section.
Then I get thinking why not take more from the front than the back, say 1/4 - 3/8 extra. That would give about 2-3 degrees of extra castor angle built in.
For a truck riding high enough in the back to take a load that would level it out, 90% of the time while driving empty its sitting about say 2" higher at the rear wheels than the front.
The front LCA cross shafts arent horizontal in that case 90% of the time. In fact the suspension is leaning forwards, the pitch centre is raised and probably promotes dive.
I guess a lot of guys on here who say they came up with zero - 1 degree of castor may have that same nose down stance.
I also intend to do THE castor mod by redrilling the cross shafts at about 1/2".
Anyway if anyone can point out to me the obvious problem that I have totally overlooked I'd be very pleased to hear about it. I havent been able to find anything on it here but if anyone remembers a previous discussion it would be great to get a link. If anyone has done this before I'd like to hear about the success or otherwise.