The bike parking facility at the hardware/lumber store is pathetic, so I just rode into the lumber yard and locked up the bike to the trailer, next to a pallet of plywood, in a very visible spot. The two of them make a darned unwieldy package, hard to steal, and most people in the lumber yard are not there to steal a bike. I figured the bike was safer there than it would have been at the silly excuse for a bike rack out front.
It was fun parking my trailer rig in the yard with all the huge contractors' trucks. (I mean huge trucks belonging to contractors, though some of the contractors are rather large also.)
When I emerged with my shopping, it took a little longer to pack that it would have if I'd been driving. I couldn't just "throw it all in the trunk". But it wasn't a major effort, either.
The tall stuff was bundled tightly with bungees and tensioned in 3 directions, resting against the back of the trailer. I took time to shake it and shove it around brutally before leaving the yard, to make sure the load wouldn't shift. The guy who checks sales receipts at the gate was quite amused.
With the heavy stuff in the trailer base, the load rode very well on the mere 2 mile (or so) ride home. I confess I used my zap kit to help get up the hill, though -- there was a fair amount of weight in the trailer. I think I could carry lumber at least up to 6 feet. 8 ft uncut pieces would be more challenging -- the CoG of the lumber would be out above the edge of the trailer, and I'm not sure what it would do.