They used to do this all the time in the mid-west region right out of the supplier, however this is fine for a too the beach for the summer then return for the fall type of travel, but, if you plan on using your trailer more than this you would be wise to get a new 18 trailer and here's why. Yes the shark bite thing, which can be over come with repositioning of the boat and mast or, purchasing a longer front main tube, however take these facts, the weight is much higher if old than I think 1985, the hulls post 1983 started to get some what thin ie. lighter so the need for double wheeled or full set of hull cradles are required, even if your boat is a pre 1985 one should have this hull support system. Also with this added weight 12" wheels are the best. So if you want to do it right and keep from repairing your hulls all the time save up the bucks and get a made for 18' trailer and ad on the 12" wheels and the double support wheels, or those cradle systems. I bit the bullet after I refinished my hulls and on the very first time out I got bit and a hole in the under side trying to bring the boat back up in high winds, I learned my lesson.
good luck my trailer is a Genensis 18'