Gap Allowance for silicon?

[CThompson]

Maybe some one could tell me what sort of gap should be allowed between glass sides for silicon.

That is, a meter (for easy maths) long tank made from 10mm glass will have the bottom cut at 980mm long, but that is not allowing for the silicon itself.

Would allowing a 2mm gap at both ends be sufficient, so the bottom would be cut at 976mm?

Thanks,

Craig

[trofius]

from memory 2mm is about right for a base , a bit less for sides