I'm pretty sure a Crewman V6 auto can tow 2100kg but a manual one is only 1600kg. Check your owners manual.

So if you have an auto V6 Crewman and the HQ weighs 1450kg it means the trailer must weight 2100kg - 1450kg + towball weght. Which means 650kg + weight on the Crewman's towball so it'll be right on the limit. If it is a manual V6 sell it and buy a V8 auto, these can tow 2500kg from memory.

Guessing an approx towball mass of about 200kg, you have to subtract that from the load capacity of the Crewman too which is about 750kg, which leaves you with about 550kg load in the Crewman. So say you have 300kg of people (5 x passengers) you can only put an additional 250kg in the car and this will include fuel, towbar and any other accessories on it. So if you are planning on towing the HQ and load up the Crewman think again!

BEFORE you even think about towing that much with a 4L65E auto you will need to get an auto transmission cooler fitted, and i'd also recommend getting the tranny fluid flushed and put synthetic fluid in it, it runs a bit cooler than the mineral stuff.