I'm considering modifying some of my shallow cranks by converting them to coffin style flat bills.  Would this approach work or would it throw off the action too much?  

I think it’s worth a try and truly, there is only one way to find out. You might come up with a winner. ?

Depends on where the tie is located s how much is cut off, it’s critical for diving bill to perform correctly.

Tom

I've done it, and it can work well, but not really worth the effort with all the great cranks available.