Neil - That's a whitewater river kayak you've got there - a high volume "creek boat," in fact (though it may not have been thought of as such when it was conceived, depending on just how old it is). Nothing wrong with that, but those boats are designed to turn. On a nice flat lake, or bay, they don't paddle in a straight line worth a darn, so don't get discouraged if you find doing so is problematic . . . paddling is still lots of fun!
Plus, you don't have to worry about scratching it, or even slamming into the occasional boulder!

Dave
PS - you might just be able to shove that foam bulkhead further up into the hull, rather than do any cutting.