If you're having such annoying experience with this, why not just add a water key where necessary? I added Amado water keys to the 1st and 3rd tuning slides of my 1924 Eb tuba because I got tired of pulling them so frequently (I think it would make an excellent condenser for a distillery). They were easy to add, are out of the way, and work well. Adding a more conventional water key would not be substantially more difficult. Any tech should be able to do it in about 20 minutes.
Gary Merrill
Wessex EEb Bass tuba (DW 3XL or 2XL)
Mack Brass Compensating Euph (DE N106, Euph J, J9 euph)
Amati Oval Euph (DE 104, Euph J, J6 euph)
1924 Buescher 3-valve Eb tuba (with std US receiver), Kelly 25
Schiller American Heritage 7B clone bass trombone (DE LB K/K10/112/14 Lexan, Brass Ark MV50R)
1947 Olds "Standard" trombone (Olds #3)