i just completed the "TED MOD" on my Vortex- the S- coil uses a 5/16-24 thread. make sure its the 5/16-24. its a fine thread. you can find a tap and proper drill bit online or ebay. Pep Boys auto store has a kawasaki brand tap and drill pack for 3$. the tap is easy to find but the drill bit size is a size "I" (whatever that means?...) so to make life easy i got the pack with both in it. i would recommend a drill press so the holes and tap are straight but i guess if you take your time you could do it by hand because your just following the old hole. i drill with the slowest speed on my press. when i put the tap in the drill press to make the thread i Dont use the motor on the drill press. i just apply light down pressure with the press handle and turn the tap by hand slowly using a drop of oil . make sure you drill and tap the black quiver mount plate first and then the crossbow hole. you SHOULDNT do both in one shot . i used the hole closer to the forearm stock. when you screw in the LIMBSAVER--- 4 1/2 inch S- COIL it snugs up nice almost against stock giving a better feel and more stability. the aluminum is a little on the thin side but seems like it wont be a problem. if it gets loose down the road you could just pop the black cover cap from the front of the channel of the crossbow and snake a 5/16-24 nut taped to a rod to snake it down to the hole. all in all- i think this mod is better than tapping the plastic forearm. i guess its also gonna help a little with shock and vibration too! also i plan on leaving the handle on at all times so thread life wont be a problem. this makes it a little tight in the padded case but works. thanks for the idea Ted! WHAT A COOL MOD!!!!!!!!!!!