The best thread to use would be Tenara (goretex) but it is very expensive and it isn't actually as strong as polyester. I am a little in the air whether the difference is worth it, especially if the tramp is covered most of the time. I have fixed several tramps and made some for my 31 and have not had a problem (but this is only within the last year.. time will tell). I use size 19 needle with v-92 thread wil a sailrite lsz1 machine. It can be difficult if you are going through multiple layers and probably need v138 thread though I have never tried it.