Not that flimsy. Kel Tec has been making these for a couple of decades, so any early issues have been corrected. I have both the P32 & P3AT with the extended mags for both.
On the .380, I prefer the flush fit mags & discovered that the extended magazines are simply regular magazines (the steel part) with the extension being cast plastic. I removed the bottom plate (& spring & follower of course) then carefully cut the extension off. I trimmed the spring to the length of my 6 round mags, and reassembled it with the base plate fitting the steel body. So you can go from extended to regular flush fit—-but you can’t go back.