Trial fitted brass fittings into tank. Only the small 1/8" NPT fittings actually engage the pre-tapped holes in the fuel tank more than 1/2 to 3/4 turn with most of pipe threads still showing. I had a 1/8" NPT tap and with very little effort was able to chase/cut threading a little deeper. Got the 1/8" fittings to seat over half of thread length. Couldn't get the 3/8", 1/4" fitting to screw in at all. I ordered some 3/8", 1/4" NPT pipe taps off internet
While waiting for the taps, I started by taping the holes in fuel tank with masking tape, poured in two cups of acetone and started sloshing the tank. Pressure built up quickly due to the volatile acetone and loosened the tape seals.....acetone everywhere. Decided to follow other instructions which said to use NPT pipe plugs to seal holes. I found a local plumbing store that carried the plugs but of course they had every size except what I was looking for. I ordered a set off the internet for 1/3 of price for special order from Lowe's or Home Depot. Amazon lost that package and had to re-order.
When both orders came (taps and plugs), I set to work. I spent almost an hour with short 5" spanner trying to work the 3/8" tap into the hole. I tightened, loosened, tightened, loosened trying to cut threading deeper. VERY slow going. Sent text question to KitFox AC asking if permissible to cut deeper threads on Saturday morning. Didn't get answer until late Monday morning. In meantime, I had pulled out a 12" spanner and really leaned into torquing the wrench/tap to cut the threads. Took almost 40 minutes putting more and more pressure into torque before i could finally seat the fuel outlet/strainer more than 4 threads. Second tank went quicker because I had learned I wasn't going to crack/split fiberglass in the area. Only cut threads maybe two full turns on tap which got very warm due to energy to cut the fiberglass resin. Then got call from Brandon at Kitfox who said OK to cut deeper but not too deep as when sealer placed, would act as lubricant and fittings would seat deeper.
I placed the plugs with teflon tape to seal and repeated the acetone/gas rinse on the right tank. All went fine. Then moved to left tank.....oh, noooo!!!!.....fuel lead in corners where "lid" and "tub" portion of tank meet. Took pictures and sent to Kitfox. Brandon called hour or so later and said would have to send new tank as leak was not repairable. Special fiberglass resin is necessary to avoid degradation by fuel.