Luc---using a 7T valve in the RV14 'can' be done, but it will take some creative tube bending to connect the wing tubes to the valve. The 7T with the 90* elbows facing aft are at 45* to the tunnel sides. That means that the 'original' designed wing tubes would have to be changed to matched the new valve configuration. Its pretty tight in that area.
The bend after the flare would have to be very close to the aft side of the nut to clear the sides. An "S" bend back to center the aft to mimic the original design.
Grab some extra 3/8 tubing to make some patterns. Eat lunch first, you may be there awhile! Best plan is to stay with the 2T valve that Vans supplies.
Tom Swearengen, TS Flightlines LLC
Teflon Hose Assemblies for Experimentals
Proud Vendor for RV1, Donator to VAF
RV7 Tail Kit Completed, Fuse started-Pay as I go Plan