I upgraded 2 V2.1 and 2 V3.b to V4.2 using upgrade kits from them.
Kit came within. Wk via DHL and the upgrade itself took about 40min/light using the online guide.
Be ready to supply your own thermal paste (easy to get on Amazon for $15), and a bowl to keep all the screws and spacers.
Upgrade went fine. Typical IT challenges on startup similar to setting up any other wireless gear (sometimes it just works, other times it takes a few tries).
In the end I ended up saving about $400/light due to the low resale value of older Gens.
Kit was about $300ea if i remember right and I paid about $350ea for the used lights.
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