HVAC in small iso booths

Hello everyone, I've been having some meetings with my HVAC contractor, and we're really trying to figure out what to do with a couple of small iso booths (4X8 and 4 X 6 feet with approx 9 foot ceilings) Is everyone doing a send and return to these size spaces? It seems like there would be extreme heat / cold (I understand that we could but some control on the inlets) by doing so. Maybe just a return? Or nothing at all (which seems like the space would get quite warm, especially tube guitar amp in the room, etc. The building is in Michigan, so we have weather extremes (90+ F temps for the last two weeks, and a winter that might be around 0 for weeks on end). Thanks again Brian Michigan