I love cross valves.  The only problem I have seen is when sanding
the seats with fine sandpaper never press too hard or it will warp
the aluminum seats bending the points of the crosses into a different
plane than the outside arms of the crosses and causing leaks.

It is unnecessary to increase valve travel for the larger pneumatics
in a Duo-Art stack.  0.035" is the optimal travel for all Aeolian
valves, and most other brands as well.  0.002" variation is acceptable.
Never allow less than 0.033" and never more than 0.040", so your
0.039" is acceptable.

More travel than 0.040" can allow too much air into the system during
repeating notes.  Less then 0032" is likely to make pneumatics to close
slowly and open too slowly as well.

Doug L. Bullock
http://thepianoworld.com/