The Overhang is a non issue for modern fdm printers, and printing on it's side hides layer lines. Splitting it just creates more seems....
I've printed this waveguide several times with zero issues.
Okay, glad that worked for you.. but I have a different set of goals than you and have these concerns with printing this in its side.
1. Printing it on its side is going to require supports.
2. Printing perfect holes at an angle or from the Z axis is very difficult even for modern FDM printer (resin too) and I want that tweeter to fit in perfectly
Also I like to think I have a modern printer as I have built 3 and designed my own custom parts for each and released them…
Anyways here is a first quick test run.. need to work on that lower part overhang (probable slow down the external perimeter a bit) but I think it’s going turn out fine.. also planning to possibly print a few layers on the lower half in a separate color which might look cool.. either way, the filament I want to use will be here tomorrow so will wait for that before I test again and post any more pictures or update.
edit: added pictures and cleaned up writing a bit