The MX jib was a solution for down wind sailing in sloop mode configuration... If you plan to use the spin for down wind sailing... then... no need for the oversized jib. (it actually would hurt you) You also get to dump the barberhauler system.
Maximizing the jib for upwind sailing means you will go with a higher aspect jib which allows you to put self tacking hardware on the front beam and clean the tramp up considerably.
If you are keeping the standard jib... then you can consider sheeting to a couple of points on the tramp.
if you plan to use the mx or standard jib and replace the inboard sheeting system with grommets... Make sure you upgrade the tramp material to handle the loads and have a means to really tighten it up. The Aussies used a really thick tramp mesh and were able to really tighten the tramp up from one side and the rear without pulling it out of the boat on the Tornado. If you don't get the tramp almost rigid... energy is lost from the jib stretching the tramp on each puff.
Finally, you should consider your sheeting point for the spin on the boat. It will be determined by the spin cut and luff length. Possibilities include the shroud attachment point. the existing jib track or the tramp lacings.
Reinforcing the front cross beam is very important. The shape and the size of the beams on modern spin boats are much bigger then the P19 section. Big beams work to keep the boat stiff. You might consider a new third party front beam since you have the decks off already. A carbon tube from Australia is remarkably cheap (i am told) and could solve your problem.
Note the comment about finding room to attach a spin pole end fitting on the front beam.
Note.. the buoyancy of the P19 bows is not great and so keeping weight out of the nose is important.... not having to go with a nacra type bow foil is important.
Finally... every P19 I have sailed had these cracs in the deck in front of the dagger board wells. Everyone reports that this fix is a pain in the butt. Take a look at this spot.
