WacoFan
Bigly
All of the variable costs are deductible, just none of the fixed costs. So you can't deduct things like hangar space, insurance, or annual inspections, but you can deduct anything that you pay as a result of doing the flight, such as fuel and FBO ramp fees. There's some disagreement among accountants on whether you can deduct engine and prop reserves, but most seem to believe you can, and I doubt the IRS would make an issue of it.
Set your plane up as an entity perhaps - perhaps limit liability and you can come up with an hourly rate including reserves, some allowance for fixed costs, etc and "pay" that amount to the entity when you fly - be it PnP or not. Plus, if you sell the Mooney to upgrade to a 195 the entity is selling it, so if some Bozo crashes it on the way home the entity is a potential target, not you personally. Of course talk to a lawyer, I'm spitballing.