[Thunder Chicken]

Here's a million dollar question!!
Is there a bit of a guideline to use when trying to decide on a engine size to an airplane's weight? I've tried searching for some info, but dident come up with much.
The reason i'm asking is I want to build a twin SPAD, a sort of cl-415, and want to use 2 .46 i have, but dident know the max weight i should keep it under.....looking at some other twins out there, seems 10-12 pounds for those 2 engines would be about right.
If there are any charts out there that shows this sort of info, that'd be great!!

Thanks!