The maximum towloads specified by the car manufacturers normally do not differentiate between a caravan and any other type of trailer. Because caravans are big and boxy, it's not advisable to make full use of the limit, especially when it exceeds the kerbweight, but for low loader trailers it would be absolutely no problem.
The 85% figure is only a recommendation, primarily for those new to caravanning, but, where the towlimit allows, an experienced caravanner can go up to 100%, depending on his/her level of experience and confidence, without undue risk.