First of many questions (Rocker replacement)

[72longstepper]

I bow before all ye body/fender masters. My 72 year old addled brain is lost.
Pics show where I am at on LH side with RH side still waiting on same operation. Questions are as folllows:
1. How much or how little of the OS floor piece do you have to use? Floor is solid front and back.
2. Braces under floor are solid so can I just cut what I need, keeping in mind the holes for front brace etc.?
Corners are in good shape (can I cut that end and just weld it at the back?
I have the Eastwood 135 (110). If anyone else has this model what settings work for you.
Anything you can add is GREATLY APPRECIATED.