No I am not using 18650 individual Cells - I am using a complete single 3S Lipo battery solution. I am not using the Windcamp commercial solution, I am using a solution created in VK-Land by VK3YY and I took the connectors from one of my defunkt Yaesu NiMH (FNB-85) put that on my AA battery cell case and took its cable plus two 100k resistors(voltage splitter for the green "do not allow charging via the external 13.8v socket, lead) for the Turnigy Nanotech 2500maH LiPO battery from Hobbyking. I then put rechargable eneloop cells in the AA case. this pacjage with the eneloops last a LOT shorter time than the LIPO but it’s a backup. I would expect you may see the same with the 18650s.
As you say there are also commercial options from Windcamp and I think direct out of China if you wish to pay extra for the convenience but to manually do this is simple.
In my case I remove the battery to charge it so no changes are needed to the battery compartment cover.