I'm putting this together to donate to a Fraternity, so a couple guidelines are: minimal money & time. I don't want to build a cab (been there, done that, not this project).
So an MKII, a midway Blitz, and Nintendo widebody are Greater than 25".
Hmmmm, those sound like newer cabs, ie: harder to find used & cheap.
Out of curiosity, what is the opening on a Defender cab?