Moving the tank vents is one of the most basic jobs of a control line builder. Your life in CL will be a lot better if you give up trying to live with tanks as they are and resolve to make the vents the best they can be for every project.
Soldering iron, torch, solder, flux, 1/8" brass tubing, a drill, a box of baking soda. Not too expensive, but essential.
I play it safe and have engine feed, uniflow, muffler pressure and filler vents. That way I can test fly and plug the ones I don't need. Also, I position the filler vents so I can gas up in car position and not hold the model at funny angle. To really get smart, position the filler so the overflow misses the model.
The picture is a 30-year-old model in the chop for a 5-year rehab. The 50 cc tank worked OK, but it was a little too small. I'm going up to 60 cc with and old Acme tank.