My 500/4 sidecar outfit apparently has 6" pre load spacers, fitted by previous owner, result is good to my mind with 100, 000 miles put on it by me and no sighns of bottoming out, even with meon the bike, the wife and camping gear in the chair and riding a bit like a pillock (hit a ton on the Merthyr Tudfyl streight bit of A470 heading towards Brecon. Yes, downhill with a following wind) I've also carried complete 500/4's in the sidecar and 90% on a bmwr80 on another occasion. However I think 6" pre load spacers might be an exaduration. I've not opend them up to look myself.Proper uprated springs would be most peoples reccomendation. I'm tight so I'd bung in a 1" slug of and see what effect it has, I also have a lathe as being tight I added up the cost of bits I needed to fix a few projects and worked out the thing would have cost me next to nothing once those jobs were done which is a rather extreme version of tight.