I know this thread is over a year old but I was wondering how well it worked out, and if you ever got around to adding a downward radial system made from just wire, maybe with alligator clips to the antenna base (and a brick or ground stake for each lower end?) to give you quick assembly once parked?
Sorry for he late reply and thanks to Connor for posting the video link. The antenna worked really well and stood up to some fierce winds without any problems, however I've moved on from that installation, firstly I bought an MFJ 1979 17' telescopic whip antenna, and whilst it cost a fair bit more than the silver rod, it's very lightweight, well built, collapses to a couple of feet and most importantly screws into a 3/8 stud mount.
Secondly, I discussed the Scorpion SA680 that I missed out on, well the chap that bought it was short of cash and wanted to sell, it took me a nanosecond to make the decision to buy it this time. So the car now sports a rather large screwdirver antenna on a large custom built and strengthened trunk mount.
The mast that I used for the original antenna is still in use, I sometimes attach a 2m halo antenna for SSB work, and if I'm feeling really adventurous I mount my 8 element 2m beam.
I still have the silver rod and haven't given up on using it for something else, it was cheap and an easy mod to carry out, a big performance improvement over the mobile antenna