I am making cabinet doors with 1/4" Birch plywood panels grooved into a
Poplar frame.

I was wondering whether I still need to keep the panel floating if it is
plywood since plywood is relatively dimensionally stable and since it
will be aligned with the grain of the Poplar frame along the stiles and
rails.

So is it ok to glue? Or must they float?
(Or is there a middle ground where say I can put a dab of glue along the
mid-section of each of the panel sides)