I wouldn’t call myself experienced, especially comparing to same folks here, but please consider :
- S21A is wider than S2, so the TIR optics and reflector will be too small (narrow)
- 10507 Carclo will be to to narrow too. You need around 23mm diameter to fill the whole S21A width
- TIR is lower than reflector, which generates additional gap to be filled. You should either make a distacer by yourself or buy one of available here (user kariba-ru for instance)
if this is your first build, consider single led - easier and cheaper if failed. My several first builds were awful. Now around 200, but watching guys here, still lots to learn
IMHO: S21A is still chalanging in modding due to few spare parts on the market. Reconsider if this is what you want to start with. But if you are skilled and experienced in soldering - why not to give it try?
