I don't have the equipment to do this, but here's my thought on HST and abs: Just use one or two weight increments, but increase the incline each mesocycle. Hypothetically: Body weight, 5 lbs, 10 lbs (behind head) for 15's. For 10's, same progression, but incline, 10 - 15 degrees. For 5's, same weight progression, but incline 20 - 30 degrees. Post 5's, keep the same weight progression, but up the incline steadily.
Do you all think that would work out ok?