Replacing outer sills on car

[Nuts-about-cars]

I might be replacing the outer sills on my car, it's a mk2 Cavalier, and I'll be using full sills, not cover ones, and I was wondering if you need to brace the door apertures before you cut off the outer sills? I won't be touching the inner sills as remarkably these are not rusty (at the moment!) so that should still offer some structural rigidity I would have thought, but I may be wrong, and I guess that's why I'm asking you for your input on what you think! The car, I'm a bit embarrassed about this, when I repaired the sills orignally, I just used cover sills, I did weld them on and used loads of sealant to prevent any water from getting anywhere near the sandwich, and heavily wax injected them too, and so far, so good, they're 4 years old now and not a trace of rust, but I just have an uneasy feeling about what might be happening behind them and I can't help thinking I'd be better to cut it all off and put on full sills like I should've done in the first place!

 

[timinder]

Coincidence, but I'm doing a similar job on a Mk2 Cavalier at the moment, but just the rear parts and rear arch. inside the sill there's a strengthening piece, and the inner sill is a lot thicker than the outer; so depending on how high up the sill you're going, you should be OK.
Got any photos?

 

[BrokenBiker]

i always brace the doors on any car if i cut the whole sill off.

i made a set of braces, quite simple just get a length of pipe just ive half the distance between the pillars that will accept an m12 nut, weld the nut into an end of the pipe, get a length of m12 threaded bar the same length as the pipe, thread it in, weld a nut about an inch onto the free end of the bar, file all the edges down and job done.

simply place between the pillars, tighten enough to keep the door clearances in place and start cutting the will out