Couple of questions with my c20 rear with 12" notch

[six5]

This is my first Chevy truck build. You can get my complete run down on my build thread in my signature.

I installed my Notches today then realized I did not take in consideration how much the axle will/might move forward when it comes up in the notch. I think I have ample room with my notches. Is the vertical movement of the axle stay the same or varies when lowered and raised?

I went with a 12" notch so I could have a 1.5" bump stop and still lay my bed on the ground with 20" rims. Are my calculations right with being able to lay the bed on the ground with my notch? I will have custom lower control arms with a wishbone....

Here is where I am at right now with my truck......



Thanks

six5