[Boxtaboy]

You can run without the spare tire, but I'm not sure if it helps with any frontal crash energy dissipation or not. Prob. not, but the new 987 models although they run without them, do have a redesigned, reinforced frontal structural area to improve the crush protection of the leg/feet area.

As for the lightweight battery, unless you don't use the radio or other accessories much, I'd personally forgo that idea. With the small battery, I'd think with just a couple openings/closings of the softop without the engine on, and your battery would be out of juice.

You could prob. lose some weight by stripping unnecessary items like a rear storage box/speaker kit, front lower center console (GT3 console delete), that shelf that holds the owner's manual located below the steering wheel, etc.