for a -110/-105 situation that risks $110, you'd need to bet this:
-110 bet $1,600 to win $1,455
-105 bet $1,565 to win $1,490
If you don't win, you'll lose $110 either way, but when you win, you're now cashing about $2,945 per middle - in the examples used, you'd still be losing $10,670 on 97 losses but would now win $8,835 - still a losing expectation here. At -102, your middle profit escalates to about $3,708 per middle, or a profit in 3 wins of $11,124, now a positive expectation. So 12 points looks to be the positive number for a pure middle situation if the 3% win rate is correct, and anything less is of course more desirable.