I just started my second 2x day MWF routine. last time I did the same workout AM and PM, so the squat and deadlift was alternated. This time, I am doing it the way Bryan suggested and doing workout A (squat) in the AM and workout B (deadlift) in the PM. Strength was good last cycle with a 40 pound increase in my deadlift.
I have only done the two workouts yesterday and strength was not an issue, could be because it is only first W/O in the 15's. The DOMS is the worst I have ever had it at any point through 4 HST cycles though. It's not severe though and will not prohibit tomorrow's W/O.
I would start with low volume and see what happens. I did one set through the 15's, one set in the 10's, 1-2 sets in the 5's, with a drop or burn set of 8-12 reps. I may have been able to handle slightly more volume if I had not been olympic lifting TuThSat. I did gain 7 pounds though.
I agree with Totentanz, at least 6 hours between W/O's. In the 5's and neg's it helped to take a short nap before the PM workout. You REALLY need to eat if bulking though.