The first thing to try is to take a couple zip ties and secure the two halves of the screen together, which improves the VHF gain.
I don't think you'll have much luck with the Antenna Direct VHF kit. It's designed to clip onto the back of narrower reflectors that don't pick up anything at VHF frequencies, while the reflector on the 4228 does pick up some VHF, probably more than the kit will.