Hi - the suspension units on the combi trolley need to be replaced and I'm guesing that units rated at 350kg for the pair would be suitable - nominally 150kg for boat, spars and foils, 150kg for trolley and trailer- 
does that sound reasonable for the boat? I know min weight is around 100kg but is that just the hull or hull + spars+foils?
Thanks

why not ask the manufacturer or sovereign - my new units were softer than original and give a smoother less choppy ride, whereas my wayfarer plus all the gear needs something (quite) a bit firmer

Unfortunately, I think the manufacturer may be long gone it has a RAPIDE badge and I thing the remanants of an Aldridge Trailer XXXX manufacturers badge.

Sovereign may help - I can weigh the road base at a push, (As it's not one of theirs) but the weight of the boat is trickier to determine. 
- thanks

Speaking to the trailer re sellers, it seems as though the road bases are often specified to cope with the heaviest dinghy likely to use that road base, and therefore may be quite a bit more than a Merlin. That might expplain the 'choppy' ride experienced.

Having difficulty finding a direct number for Sovereign.

96 kilos + mast, boom and sails.

sorry, plus rudder.f

sovereign trailers=www.welshharp.co.uk

Thanks Jon and John, I can get a pretty good idea of mast/boom weight and the rudder tiller assy, to add to the 96kg.

I'm more optimistic the weight capacity of 350kg will be correct. It would have been easy to over spec the weight and go to 550kg, then rattle the old boat to bits while towing.
Apparently the suspension units weigh 30kg by themselves, and the 350 kg units are the same as the 550kg units but with longer arms.

Thanks yet again for the help on the forum.