Replacing carpet with 3/4" hardwood. Under the carpet is a mix of old
floors, including lineoleum and maple in bad shape. Solid subfloor (doug fir
planks---old house).

I can't do 1/2 or 3/4 inch plywood then 3/4" flooring---makes the floor way
to high. What about 1/4" plywood for a nice flat surface, then nailing and
stapling through flooring, through 1/4 and into original subfloor? Most
manufacturers require 3/4 inch plywood beneath flooring.

Engineered flooring is an option, but I'd prefer 3/4" for my historic house.

Thanks. B.