What I do is not worry about total advance at first, instead with the engine warmed up I start adding timing to see what the engine will take without the starter kicking back.. The more initial timing you can give it the better it will launch... Your not looking to rev the engine above 3000 rpm here just see what the starter will take & see how the car comes out of the hole... So now you know how much initial lead you want & you just need to limit the total to around 34-36 degrees

This chart may help...

Modifying advance slots
degrees / slot size
6.............. .340
7................355
8................375
9................390
10...............405
11.5 ...........420
12...............435
13...............445
14...............460
15...............475
16...............490
17...............505
18...............520