There's quite a difference between 11 meters and 2 meters. Now, I took an OLD Turner Signal Kicker 11 meter mag mount and cut it down for 10 meters. Works great for that purpose. I'll bet you could build something that would go into the mount for the 11 meter antenna pretty cheaply.
I removed the coil and trimmed down a mag mount 11m whip for 2m. I also wrapped the magnet in copper tape that had conductive adhesive and soldered the coax shield to it. It sat on my tracker until the Transmission died. Now it sits on a metal heater with a cut off coax. I need to fix it but I need parts so I'm waiting for a hamfest to save shipping on small parts.
To N6TPT: I can't believe I said 11m to 2m. I meant 11m to 10m. I bought a 10m and a 6m antenna at the same time. Both came with whips the same length, and included a small paper telling how long the whip needed to be, so the customer could cut the whip to match. It said to measure from the "ball end" of the whip. But not a word about the second point of the measurement. So, my real question: Where is the second point? (1) Bottom of mount? (2) Bottom of the coil? (3) Top of the coil? (4) Top of the holder where the set screws are to secure the whip? I guess I could cut them (10 & 6) long and go by "trial and error." I am made to think that the second point is at the bottom of the coil, since the coil and the whip holder are all electrically connected. Comment?
To KK4QBY: See my comment to N6TPT above. Yeah, I see what you describe. I suppose one could use almost any piece of metal that will radiate, and keep adjusting until the SWR is within range of the output parameters. When I was a Novice, I used a TV mast, adjusted to length, sitting on a glass insulator, braid side of the coax attached to a ground rod, and no radials, using my old DX-40. Got a doctor in Venezuela for a long ragchew on CW.
FYI, Firestick does offer a 5/8 wave 2 meter Firestick antenna. I used one on a Van with west coast mirrors. Its 4 Ft long. They also sell a Scanner antenna in a 4 ft fiberglass whip. http://www.firestik.com/CatalogFrame.htm
What? No spreadsheets documenting SWR curves over a frequency range before cutting the antenna? No Smith Chart discussion? Field strength measurements and analysis? No Eznec prediction charts and antenna simulation graphs to ponder and speculate over? Where's the 26 pages of hams posting their own insight and conclusions before attempting the modification? Sigh....
Ok, 11m to 10m not 2m... Doesnt the Firestick have an adjustment screw on the top to fine tune it for 11m? I would just peel back the PVC covering at the top. unwind about an inch and a half, then Re attach the wire end to the adjustment screw assembly, and check SWR. Then if needed I would snip off an additional 1/4 inch till I got it where I wanted it, and re cover the end with some shrink tubing.... YMMV