Not to just re-iterate what everyone is saying, but you always want to be heavier if you can't be just right. Your old BCD was buoyant, and your new BP is about -6#....so overall you're probably gaining 8# of negative buoyancy switching over. You were at 19 pounds? Start of at like 13 or 14. To be more specific:
I'd take: 4#, 4#, 3#, 3# on your belt the first time with 2x2# on the boat.
After the first dive, with your empty tank, check your buoyancy. See if you can't get someone on the boat to help. Maybe pull your weightbelt off so you can change weights easily and just hold it for ballast. If you tank isn't empty, and you're diving an AL80, then get neutrally buoyant and add like 5 pounds.
Another option, to gain pool access as above, go to your LDS and see if they're doing a pool session or Discover that you could jump in on. Might cost you $20, but it could make your trip better. Of course if you're going salt water, then pool dives don't help too much.