Hello DazBaz,
Weight ratios are of course important but they are not the only or necessarily the most important aspect of achieving a good outfit.
Your proposed outfit will have a ratio of 95%. This is fairly high value and exceeds the industries guidance of 85% for novices. usually a couple of percent is unlikely to be a problem, but 10% is worryingly high for novice tower.
Even though you may intend to keep the caravan below its load limit, this will not show up in the way the towing ratio is calculated which always utilised the MTPLM/ kerbweight.
Crazy I know, but that the way it is. From a purely practical way, yes under loading the caravan will move the real ratio in the right direction, but it still seems on the high side.