I think that ID had a problem with his Imax when he tried to isolate it from the mast. Dunno if he had radials on it for sure, but if it was the OEM ground plane kit for the Imax that well could have been the problem. AS we know, they aren't even 1/4 wavelength long. They are 6 ft long only. But isolating the Imax, using real 1/4 wavelength radials, and adding a 4.25 inch diameter choke with 5 winds of RG-58 is known as a success formula for the Imax. Maybe not as optimal as a Maco V-58 or a Super Penetrator, but that will be the best one can do for the Imax.
I considered getting some 10 ft of threaded rod that has the same size thread and diameter as the radials have. Cutting the threaded rod into four 2 1/2 ft pieces and adding one piece to each radial will make them 8 1/2 ft long - which should behave like a real 1/4 wavelength radial would. This might prove to be a real cheap fix; certainly cheaper than buying four steel whips for sure! Haven't done it yet, but I might play with that idea sometime this Spring. Just some thoughts . . .