Many thanks for the feedback thus far. To answer a couple of the questions posed:
1. Single phase
2. There is one 90-deg sweep at the end of the line where it turns into the barn. I'd already resigned myself to digging this up so I could pull the wire in a long straight line before hand-feeding it through the 90 and into the barn. From what I'm reading, however, that may serve only to complicate the job.
3. The local electrician I've consulted says "#2 aluminum" is all I can use. Not sure how to interpret that. I'd like to derive the most power I can from the trench I've inherited--digging a new trench is not an option--but clearly don't want to run the risk of melting an oversized wire to the conduit, as one of you pointed out. Yikes.
Not sure I am code-current, but Virginia, Aluminium isn't even allowed for a residential subscriber's use past the initial entrance. Powerco or industrial, only.
The proper alloy, proper prep, terminations, protective paste chemistry, it can be 40+ year trouble-free. Powering this PC as we speak. As far as the panel, anyway. All Cu thereafter.
OUR side of the entrance, we Chikn's, nor even our "residential grade " hired sparks are not trusted to DO that to Powerco standards.
I'm good with that.
I pulled four "grandfathered" Al runs out of this house early-on - just on general principle. Wise move, as every one had also already gone problematic and was headed for worse.
Al needs to be done professionally, and to a very high standard, better-yet, not at all. Powercos understand it and manage it well. Good on 'em. Not enough Copper to go around, and Al is far cheaper even if there was.
OUR expertise? "Spotty, at best." Seldom worth the risks.
IF.. that sparks could not show me chapter and verse as to WHY I could not have THHW Copper instead of Al "service entrance" premade? I'd be having a coffee with head of Code Enforcement over at the County HQ, same week.
2CW