Yes, I realize you can do similar things with endo and a slower standard, but for a variety of reasons I am avoiding that path. The slas is not used, just stuck in there for crit padding. This is for quickly moving through the battlefield looking for those killing blow points. You can add that sixth mlas, but I don't like how much that leaves you underweight.
Maybe ditch the small laser entirely, shave some leg armor and fit in an additional MLas? Won't give you a ghost heat penalty, not too much hotter, and gives the same desired "crit padding". I must say that this is more of a theory build as I don't own one of these. I also shudder at the thought of and XL engine in a T-bolt. Do you find it durable enough with the armor and structure quirks?