Is valve shrouding a concern in a 318 w/ 2.02 & 1.6 valves

I already have a 318 block and crank. I need 15:1 compression, but I don't know if I can afford the custom pistons though... :/ So you can reduce valve shrouding by running smaller valves or by reworking the combustion chamber and notching the cylinder walls? How much space do you need between the cylinder wall and the valve to avoid shrouding?