Thanks - and yes, Buck is very inquisitive. He was shut out of the paddock for the majority of the time because I didn't want him underfoot while we worked. He's the same way when I go scoop manure out of the pasture or do any kind of work out there. I consider it a sign of intelligence - a very annoying sign of intelligence. I do like that catching him to ride him is a matter of him seeing me and coming to the gate, though.
We built the shed out of scrap lumber and metal laying around the property - our only cost was screws. In a few weeks we'll be putting some walls up. I saw horse poops under it when I went out this morning to ride him, so I know he's stood under it at least once.