Been quite.
I was out mowing a couple of acres with brush cutter with air conditioner on. The cab started to get warmer. Back in the tractor shed I measured the output of the AC at only 12 degrees below ambient. I had previously cleaned the screens and the radiators "looked" clean. However, upon closer inspection, I found the AC radiator clogged up completely in the area behind the battery. The material clogging the radiator was light gray and not visible unless the battery was swung out of the way and a light shone behind (between) the radiators. I could swing the battery far enough out without removing battery terminals, so this area is going to get better cleaned in the future. I plan on making a side squirting water spray wand to get in there.
This is a piss poor design feature. I was thinking of adding a thermostatically controlled fan on the front of the AC radiator, as there is no shroud to help pull air through this directly. Can't find a fan thin enough and there is very little room to fabricate a bracket to position an aux fan. The shroud would also be a poor idea as it would restrict flow into the main radiator from the sides etc. I'm still noodling on all this, but I really would like to add a fan to improve AC efficiency.
One possibility is to make more room for the fan by switching to a physically smaller battery - - a LiFePO4 may well work without giving much up in battery capacity.