For single deck game, I always try to find tables with as fewer people as possible.
I always prefer to sit somewhere in the middle because:
1. If I sit down at first or third base, when other people join, I'm less likely to find open spots to bet two hands.
2. Third base tends to draw more heat due to pit boss stereotype and ploppies' wrath.

I just read the "Blackjack First Base Penalty".
https://www.qfit.com/card-counting-fbp.htm
"In an extreme case (seven players), the advantage difference between seats 6 and 7 is about 0.05%. You lose another .05% per seat as you move toward first base. However, the difference in advantages for a card counter between first and second seat is much worse. First seat can be as much as .16% worse than second seat."

It says in a single deck, face down game, 7 players at the table, sitting at first base is much worse than third base.
It assumes 7 players at the table, only two rounds are dealt. I guess the reason behind the tens splitting penalty is only two rounds are dealt.
However, in case of a mediocre penetration, when 4-5 players at the single deck table, two rounds are dealt as well.

Thus, when two rounds are dealt, 5 players at the table, is the odds much worse or a little worse to sit at the first base compared to the third base?
It's more of a theoretical than a practical question. We don't intentionally sit at a table where only two rounds are dealt, but sometimes people join and it happens.