Only one thing you could do, is to use the nipples that allow the hammer strike them squarly. Trackofthewolf has about all the nipples necessary to get a good fit. Nipples that are too short for Pedersoli's design might cause the hammer's anvil to strike at an angle, ie: the fornt of the nipple or the rear, not squarely on the circle. That is not good. If striking at the front, it will direct gas and cap fragments to the rear. If at the rar, it will direct gasses forward, which is not bad in itself, but the rear of the nipple will pean from hammer blows and make caps stick.

Personally, I'd use a short a nipple as possible, even a pistol nipple so the fences would be operational and replace those stock hammers with a English designed hammer of the correct 'throw' for that short nipple.

Note the hammers available at Trackofthewold - everyone has a catolog, don't they? In the catolog, the pictures are full scale(size). Measure the throw needed on your gun, then find a muzzleloading hammer of the proper throw.

To find the proper throw, you measure from the centre of the hammer's screw (centre of the screw) to the centre of the nipple. That is the throw. Match it up and you are away. You might even find a true English design that is the correct throw. Some are engraved, some aren't. The Alex Henry (I think it was) is a nice design with a long nose to curl around the fence, the way they are supposed to fit. You might get lucky.