Homemade Valves

[GP Grant <s0234576@xxxxxxxxxxxx>]

I recently added homemade valves to my Marine Band F-harp.  I only valved the 
bottom six holes and it appears to work very well - I'm blow bending like mad 
on the bottom six.  

The problem is that my harp is now playing flat.  Is that a result of: 1) 
physically having valves on the harp; 2) poor technique that has become 
apparent now that the valves are installed; or, 3) have I inadvertantly 
adjusted the reeds somehow?  

I was very careful in attaching my homemade valves to the reed plate so I don't 
THINK I got any glue on the reed, or bent the reed in any way.  Has anyone come 
across this problem before?  If so, any suggestions on how I can correct the 
problem or at least avoid the problem in the future would be greatly 
appreciated?  I realise I can retune my harp by scraping the reeds, but I'm 
really hopeing there's a better way.

Thanks,

G