It all depends on what's happening (or not happening) of course...
If you mean the back ends up too low (which can make the bike harder to turn and at worst bottom out over bumps) then you can try upping the preload but if by "a bit" heavier you mean a lot
then most likely you'll need a stiffer spring. If you're not that much heavier then the spring should be OK.
Or is it "bouncing" in a way you don't like?
+3 on Kenny at MRP. Not far it all if you're in Baltimore. He can install a new spring or just set the baseline if your spring is OK. He's a suspension tuner so this is his forte.
