Yeah, i use the crap out of Union's Plus 9000 viscosity reducer. a couple percent of that in a lo-bleed white won't screw up the lo-bleed properties, from my experience.
I've used that stuff up to 50/50 before, & the shirts cure fine. (We did an art project where we filled ketchup squirt bottles with reduced ink, then drew in an open screen & pulled the squeegee across. I still have a couple of those from the 80's & they held up fine, on white)
It will start to effect opacity, and if you add too much, the ink will wick into the fabric instead of standing up on top.
I try to teach my printers that if the ink feels too thick, it is.