Weld in flip door

[swamp rat]

I have a gas flip door from an S10 and want to install into my bedside.

I have debated the best way to approach this, should i make a circular hole in the bed side or a square hole? will a square hole be more prone to inducing warpage in the panel?

It was also suggested by my uncle to go buy a hand flanger tool, flange it and bond it in place but i don't really wanna spend any more money unless its somehow superior, already have a mig, any advice? Thanks!