I'm gonna take a shot at this. I have a pair of LP-18's as well. I have used them with 13mm Velox rim tape with cross tyres up to "35c", but with the narrow rim, it ends up closer to 31-32c. I ran those tyres at 3.2ish bars or 50-55ish psi. I usually ride on "25c" aka 23c Paselas at 110 psi, but I weigh 140lbs. I know that is high, but I have rough roads where I live and pinch punctures are a common problem.I have never had any problems with the rims, but the '80s Weinmanns that they replaced had what I assume to be a defect. On the inside sidewall of the rim, the join/weld where the rim was joined to make it round was filed flat, but didn't follow the profile of the rim. The edges were sharp-ish. I think that the combination of this along with the wider than recommended tyres are a possibility. The aforementioned pear shape of the tubes also probably play a role. The wide rim strips may be hiding the bad filing.