I welcome this discussion thread. I hope others will contribute.
I my opinion, the SK68 and its many clones are excellent little flashlights for their price, but perhaps their biggest weakness is the many "halos" etc. that are associated with the low cost lens. (This appears to be a "hit-or-miss" kind of thing, and varies considerably from light to light.)
I do not know much about how to do any kind of mod, but I would welcome any and all information about how to improve the "visual quality" of the optical output from these Sipik type lights.