I do ten gal batches in my igloo. I don't go over 23#s of grain though, I can fit a tad more, but quality is better than quantity for me. But for 10g of APA its been beautiful, 1.060 grav is pushing it for me, I've done it but it was hard mixing, IIRC it was a bells two hearted?
I've done two separate mashes and combined in the end and the beer was pretty good. I boiled momentarily the first run to completely stop conversion, then started the second.
I'm also doing an AG and a extract (5g+5g) this weekend to see how that turns out of a high grav IPA for winter.