i gave up first time as well.
But its actually quite simple to back and to lay.
With back you basically say how much of a premium you want OVER the supertab price and with lay you advise how much of a premium you will pay OVER the supertab price.

both prices limited to max 30 win and 11 place

however i agree there are some improvements that i could see also.

you should see the liquidity on the Asian races like HK and SING.
huge.

and more importantly from what i have observed you can get easily supertab +10% and you wont be banned.

sometimes +15%