Engine mount box section query

[ashbudd7]

Morning everyone,

With regards to the box section for the engine mounts (I'm using the dohc) would I be ok using 45mm with a 2mm wall box or should I order up some 30mm? If I do need 30 which wall thickness should I get, 2 or 3?
It's just that a) I've found some 45mm and b)is the 30mm strong enough?

Thanks

Ashley