I really wanted to run all my Warhammers with PPCs in the arms because, well, they're beautfiul, so I'm going through and making absolutely terrifyingly hot builds for the 3 variants I own. This was the result with the 7S. My current experience with it is: Fire the PPCs until you get within MLas range, then never touch those PPCs again unless you are sure you can manage the heat from it, or you're fine with going down in a burning blaze of glory for that killshot.
For those who do not mind the look of PPC on the ST, this one is more effective due to PPC at the high mount XL version. Personally I would dump ML for DHS and cool