For people taking welchol or CSM, how are you staying regular?

I've been on Welchol for a few weeks to a month now. I'm still gradually increasing the dose when I feel like I can handle it. I'll be transitioning to CSM once I get to the max welchol dose. But I've been having trouble with constipation that makes me feel pretty much like I have the flu. I've begun taking magnesium citrate, which seems to be the standard recommendation from Shoemaker. But I'm unclear of how much to take, what timing, etc., I'm playing around with 100% RDA (420mg elemental Mg), in split doses a couple hours after meals. I'm just curious what is working for others.