Harold, I've been following this discussion and even though you don't think the slippage is at the back I have to believe that that is where the problem originates, and then maybe causes a skip on the front chain ring. My best guess is that something is wrong at the derailleur tensioner. An easy check would be to remove the tensioner completely (I'm assuming you just have a single chain ring up front) and shorten the chain as much as possible.
Almost three years ago I set up a 7 speed bike with a BBS02 crank drive for my sister. It worked okay, but since I had a new Nexus 8 speed IGH on the shelf I installed that before I gave the bike to her. I removed the entire derailleur system and did not install any tensioner. I don't remember the rear dropout details, but there was very little adjustment available, I think they were sort of slanted. Anyway, there have not been any chain issues at all. When I was visiting earlier this year the chain had a lot of slack, but still no problems, and she has to climb some 20% grades on every ride, but I did recommend she take it to her LBS and have the chain shortened. The BBS02 chain wheel is narrow enough for a 9 speed chain and I left the original 7 speed chain on the bike (don't know the chain wheel/cog sizes without checking).
I did have some chain slippage at the rear cog on my mid-drive Rover tadpole. It was hard to find, and it was set up the same as my Path tadpole. Neither one had any tensioners on the chain. Turned out there was too much boom/frame flex on the Rover when hard pedal power (on 15 to 20% grades) was being added and the fix was to add a simple (not derailleur) tensioner to it.
Don't know if any of this helps, but good luck on getting your problem sorted out.
