Same here, through cinder block wall, use all stainless hardware. 1/2" allthread, nylock nuts and washers.
On my new 3 hp 3 phase units, I put those in the attic. I made my own control panel, found some hinged lid boxes on ebay for $20( I bought a few to have around) I bought contactors also on ebay $25 each, I got same ones I have for my bay pumps, no overloads necessary. And built the control box my self and my helper and I installed everything in a day or so. Most difficult part was doing the conduits to everything. Figuring I saved over $2000 doing it myself, and its the kind of project I kind of enjoy doing. Also on this setup we pulled power from our source power for our bay pumps. I know some electricians dont like doing this, it was how it was recommended to me from several others and how we set up our previous units and have never had any problems.