Trim the spine off completely. That is just to help the metal to flow out into the finial ends.
But! Leave the tabs on for pinning the guard to the stock. One is right where the trigger bow meets the front finial. The second tab is at the butt end of the trigger bow, where it meets the stock.
If you decide to not use the rear tab, you may use a screw to hold the rear finial to the stock. I think after much use, that the screw would lose its hold in the wood. I'd prefer to pin the sucker using the tab.
