I had a situation like this on my rocket, same symptoms. The EVO wing tank is a bit more difficult to remove and I decided to try something different.
I sourced some proseal that was a bit more"fluid" then we normally use. I disconnected the exterior vent line and added as short, one foot, piece of
aluminum line and fitting.
The next step was to reach into the fuel tank filler hole and slide a piece of plastic tubing over the end of the vent line, it is just outboard the tank filler opening, and secure it with a cable tie.
I then injected some of this proseal into added short line on the inboard vent line, enough to make its way to the offending fitting on the inboard rib of the tank, then capped this end of the line.
Now the important step, and all this has to be done relatively quickly, I used air pressure from my compresser and applied it directly to the vent line. This pressure forces the " liquid" proseal into the leak. After the brief time, seconds rather then minutes, I removed the plug from the inboard vent exit and added pressure to the vent line at the tank filler end to blow out remaining proseal.
I waited a couple of days, put some fuel in, and the problem was solved. 12 years and over a thousand hours later with no issue.
Tom Martin RV1 pilot 4.6hours!
CPL & IFR rated
EVO F1 Rocket 1000 hours,
2010 SARL Rocket 100 race, average
speed of 238.6 knots/274.6mph
RV4, RV7, RV10, two HRIIs and five F1 Rockets
RV14 Tail dragger under construction #153
St.Thomas, Ontario Canada, CYQS