have a look in the toysport articles under 2tg, 3tg, 18rg tech notes. That should tell you what duration is possible for standard pistons.
I have seen one set of custom cams for a 2tg, they were around the 300 degree mark with a 10.1 lift.
The lift was not much more than stock really. (10mm if I remember rightly)
The more duration you have, the less lift you can afford to have in a stock engine.
Anyone please feel welcome to correct me if I'm wrong.