*PROCEED AT YOUR OWN RISK AND DON'T BLAME ME LATER*
1st-mark a line on the helmet from one shoulder over the top of the helmet to the other shoulder. Use masking tape and a sharpie to mark a straight line.
2nd-a hand held jig saw/saber saw and cut the helmet in 2 pieces. Roughly sand the inside of the 2 pieces so the fiberglass will have a good surface to adhere to.
3rd-use some thin metal strapping and pop rivet the 2 pieces back together adding the gap needed to fit over your head. Mine needed an additional 1/2-inch at the top, opening up to 3/4 inch at the shoulders.
******************
4th-cut small strips of fiberglass cloth, soak with resin, and apply between the metal straps. I would suggest taping some 2 inch masking tape around the exterior of the helmet seem to keep fiberglass from oozing out
5th-after fiber glassing between all the straps on the inside of the helmet, drill out the rivets. You can leave the straps in place if you fiber glassed them in place for rigidity or take them out. The fiberglass by itself is all that is needed. When the fiberglass hardens, it will be as solid as before you cut the helmet in two.
******************
6th-fiberglass 3 more layers of fiberglass cloth over the entire seem on the inside of the helmet, sanding between each coat of fiberglass.
******************
7th-skim coat the exterior of the helmet with bondo and sand to a smooth finish. A second coat of bondo may be needed for a fine finish.
******************
8th-2 thin coats of primer with some finish sanding if needed.
******************
9th-finish coat with the color that matches your helmet needs.
******************
Hope this helps, If I missed something or you have a question, PM and I will try and help you out.
10th-2 coats of "American Tradition 165833 Berry Red Gloss" then water sanded with 600 grit.
11th-2 final coats of "American Tradition 165833 Berry Red Gloss"
12th-2 coats of "American Tradition 165958 Clear Gloss"
*****************
*****************
*****************
Now, for the eyes, I have to decide if I am going to use the black lexan or a tight mesh for some air to breathe.
8)