As far as guarantee-ing profit goes, I can't guarantee anything. This is a risk service so promises cant be made. I do stake against other maxed players, so in theory the odds are 50/50. However if you stake long enough to establish a win/loss pattern things generally work out very successive from there. If you're testing your luck on one stake, you're not really leaving yourself with the opportunity to redeem your profit in a scenario where the first and only stake is lost.
Basically what I'm trying to say is, if you're only attempting at a single stake, your profit comes on a 50/50 basis. But the more stakes you do, the higher your chances are at coming out with high earnings.
If you need me to explain anything any better feel free to pm me with any other concerns or to clarify what I just mentioned.