You're like me, you want it all to fit where it won't. Just do it!
NoPro, the PCBs are shallow, narrow or narrower and all have connectors on both "component" and "solder" sides. remove the front bezels and stack/nestle an assortment of PCBs to have it all. USB and Firewire "sides" are commonly discrete and eminently cut-in-half-able for more convenient assortment repackaging.
BTW, keep the Zip! Standardize on 250 and (if possible under OS9?) upgrade to an external
Blu-ray Burner. That way you've got an entire 5.25" bay available for such a kluge in all of the PortlyMacs(R) mentioned. That's what I'm tentatively planning to do with my Zip750 kit and the optical bay of the MDD'03 OS9 Special Edition that I'm currently configuring as backup for the QS'02.
Who needs a front bezel behind that front flap anyway? Damn the ESD and full speed ahead!
jt