Seems to me that due to adhesion issues the only way to acheive a transition between Tru-Oil and lacquer would be to fully finish the entire thing with lacquer and then artfully sand back the nitro in the transition area....back to wood....then apply the Tru-Oil. I thought about trying this before but I can never remember to spray test panels when I'm finishing a guitar.
Honestly....I don't put too much stock in this working out. I think it would get ruined in the polishing stage in the transition area between Tru-Oil and nitro. I don't see how it could polish out nicely without a messy looking transition. I think the best chance would be to fully polish the nitro, carefully sand back (this would be tricky going thiough the grades), apply Tru-Oil to the bare wood, and hope for the best in the transition.What's wrong with skipping the Tru-Oil and scuffing the back of the lacquered neck with 0000 steel wool? It has more or less the same feel and it seems fifty times easier.