Hey mate,

Thanks for your interest. However a deal like that is very hard to analyse in terms of its fairness. It's very much a gambler's suggestion haha and for that I applaud you 

But the reality is I think the fairest way is to keep it at a flat fee and the way you have to look at it is that it's an investment in yourself and your own abilities to make money in the future. If my coaching helped increase your winrate by even a small amount it would not take long to recoup the investment. If my coaching turned you from a long time loser to a small winner even that it's worth every penny!

If you have any further questions don't hesitate to ask either here or via pm. Best of luck mate.