I do look at # of shots taken to handicap totals, but I feel the line has been adjusted accordingly
BUT ...
... for HT plays, I look at # of shots taken and # of fouls called as well.
If two teams have taken 44 shots each in the first half of an NBA game and have scored 105 points BUT there have been 12 total fouls called, the 2nd half under would be a big bet for me.
If we have 25 fouls in the first half, I really look to a second half over.
Another factor that is VERY important for HT plays is whether the game is a blowout, but that is something I have not been able to use one way or the other. I don't do second half totals on blowouts because I have been getting mixed results. If either game is a 15 point game at HT where the favorite or home team is winning, I don't make a play.