Medium/Low volume (depending on your definition of high volume)
High frequency
Sub-failure
If as you say, the bulk of protein synthesis occurs w/in 48 hrs of training you just need to focus on progressively getting stronger but not training so intensely to the point that you can't train very frequently.
Going by this, I aim to train a bodypart 3 times one week, 2 the next, then back to 3. But keeping work sets for each bodypart at 3-4 each session. Aiming for more weight or reps each session, eventually you will reach a point where you have to train to 'failure'. Once you can't increase either weight or reps, drop back the weight to a point where it will take you maybe 2 weeks to build back to where you couldn't increase anymore, and continue through. Or change exercise.