I'll post the obvious question which doesn't appear to have been asked yet.
Since this is gambling, how on earth can you guarantee that you will win every single session? Regardless of how good your system is, obviously there will be losing sessions.
Are you guaranteeing the 120% return out of your own pocket or is there a risk (regardless of how small) that you could lose your clients funds during a bad run?
Correct, I'll pay out of my pocket if I lose for that session. I doubt it will come to that but if it does I'll do so!
I'll add this to the OP, thanks