Very nice! If the pick up is a little bottom heavy, you don't actually need grips. What you could do is get some lead tape, like the stuff used on golf clubs to add more weight to the swing or something like that. Roll down the top of the grip, and you see where the twine binding starts? You just put a ring of the lead tape round that. I would recommend that you do a maximum of 4 rings of the tape round each section, with a maximum of 2 sections on the twine and 2 sections on the wooden part at the very end of the handle. Too much will cause the end of the bat to stick out abnormally, so 3 rings every section is a good number. Start of with 1 or 2 rings per section, and then roll the grip back up and test the pick up. After the pick up is desirable, I would recommend wrapping some electrical tape around the golf tape to keep it stable, as it can be quite flimsy, or that may have just been the golf tape I was using. You don't want the pick up too light, so make sure to test it after every 2 rings of golf tape are applied.
If this is confusing you, just PM me and I'll try explain it better, or I may post up some pics on it later!
Hope this helps!