People are buying my 3.5 AH 2 cells ( 2 in series) power packs as part of a Stenlight conversion. These are 'classed' by me as 8V series for identification and are 8.4V off charge, 7.4V nominal.
I "think" someone a while back ordered a 2 cell parallel power pack as I used to supply with my 4V series lamps, (now discontinued) "Low Voltage" to power one of Mr Biffs Duo conversions. If that person is around maybe they would like to comment.
Only thing is, as you buy, then convert, then buy Li Ion power pack, the cost escalates with each purchase and my thought is why not just buy a complete lamp.
EDIT
Yes, more has come back to me now. They bought the power pack and some XT60 connectors which I use as part of their DIY conversion. I made it clear that I could not guarantee suitability for third party conversions so they checked with Mr Biff about the voltage suitability and he OK it. Best as I remember it.