Ultimate Gambling Question

I wonder if you can help me.

I very much believe that it is possible to make long-term profits by betting on ante post accumulators in sports such as Football.

Antepost means betting on who will win the league or be top scorer or who will be promoted.

By accumulator i mean including at least 4 legs in the same bet all of which must win.

Now,I would do a whole series of these bets throughout the season.

I would also be trying to risk as little of my bank as possible.

So,heres the problem.

A very well known pro gambler says its IMPOSSIBLE to make long-term profits from such bets.

I very much want to prove(or go as close as possible to proving)otherwise.

BUT what would that entail?

For how many years would I need to show say a 10% profit before it can be said that its say 90% certain that it IS possible?

Alternatively,this works because its possible to predict short-term price movements.

Can these price movement predictions be used to shorten the proving process?

One very important thing i should tell you is that the reason most people don't believe its possible to do this is because of the size of the OVERROUNDS.

In gambling the over round is the bookies' theoretical profit on a market.

In the Premiership and English Leagues the average over round is about 28%.

I realise you'd probably need much more info but any advice /help at all would be much appreciated.

yes thats right but Im referring to their ante post markets.

For example to Win the Premier League or The Championship or League 1/League 2