Scooterotica

When using a Dellorto VHST 24 mm carb on a SIL 200cc engine, would it make a big difference if I used a 30mm manifold, instead of a 25mm one?

Stating the obvious thats a difference of 6mm which means a lip of 3mm all round.
this may not be ideal to have steps on the inlet tract of a tune/race engine but on a sil 200 I dont think it makes much difference.
Much worse to have a 30mm carb on a 25mm manifold
If you are worried about it try looking in a plumbers merchant to find a pipe/ conector to make into a stuffer to go into the manifold