Low air flow is an issue for the Enviro systems. With the Sundstrand, it's never an issue-- I can turn one bleed off, and the cabin never bumps. So leakdown might be an issue for you.
In my case, I was told that the pressurization controllers have a certain tolerance, and some of them will only go to 5.0, some will go to 5.2. If I wanted to spend a bunch of money changing controllers until I found one that went to 5.2, I suppose I could do that, but 5.0 is good enough for me. At FL280, I have about a 10,500 - 11,000 foot cabin, and that doesn't bother me.