WRJN263

I am a new GMRS licensee. I am making an ammo box repeater & have a question about the Larsen NMO 2/70. It was given to me by a friend whose Dad was a longtime ham. I know it is a dual band 2 meter/70 cm antenna with the coil in the middle. I’d like to cut it down to GMRS only, but my antenna analyzer doesn’t do UHF. Has anyone done this, and what are the whip lengths? I plan to use the 462.725/467.725 pair, so the 462 frequency would need the lowest SWR. Each of the two elements are currently around 15 inches each.