drilling chain plates?

[oyster]

My Nor'Sea 27 was made with an odd match of 7/32 wire and 3/8 turnbuckles. I'm replacing my standing rigging and am having a hard time finding fittings that match this combination. Since I don't want to downsize anything in the system, would it be a problem if I enlarged the holes in the chainplates to accept a larger 1/2" turnbuckle? This is the smallest size Suncor turnbuckle that will accept a 1/4" 7x7 (to match the strength of the original 1x19) wire and thimble for a spliced eye (remember this is an old Lyle Hess design). The chainplates are of the 1 1/2" x 1/4" outboard through-bolted variety. If this isn't a problem, then how would I go about enlarging the hole? Anyone have an objection to splices on a boat like this? You won't hurt my feelings, I haven't yet decided the route I'll take I'm just toying with ideas. However, even if I use modern mechanical terminals the 7/32 wire, 3/8 turnbuckle really limits my selection.

Thanks in advance,
Bill