I finally worked out a final solution for my piles of modules that aren't in racks...

I bought a 42ru rack: https://www.titanav.co/products/titan-av-42ru-19-adjustable-open-rack

I really like that this thing is on wheels, as I need to be able to roll it out of my studio when bands are in to record.

won't the bands want to use your modular??? are you trying to hide it from them? hahaha

JimHowell1970 suggest Befaco, which I'll look into. Are they modular in their design, or will I need multiples?

indeed I do... they're not modular and you'd need multiples - one per 2 or 3 rows & somewhere to mount them - shelves perhaps...

Also, is the TipTop Happy Ending still the cheapest way to get ears and z rails? Would it be cheaper to build my own?

I'd have thought that buying rails and inserts (or nuts, if you prefer) and ears separately would be cheapest - but don't know... also depends where you are etc... I think the b-company sell a knock off version that's cheaper...

"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia

Utility modules are the dull polish that makes the shiny modules actually shine!!!

sound sources < sound modifiers < modulation sources < utilities