[T Creighton]

Hi Jonathon,
Could I offer a suggestion to overcome your dimension problem.
Are you familiar with Google "Sketchup". It is an amazing drawing programe you can download free. It can do all sorts of clever things and comes with plenty of help and tutorials.
If you can get someone to take some reasonable size pics of a HUP for you the dimensions can be measured off the photo once it has been imported into the programme.
It is important for them to be taken square on. You would need one of each side and one front and one back. Maybe even one from above if that was possible.
You will need a reference on each photo to enable you to set the scale on the programme.
I would use two pieces of light coloured masking tape with good solid black lines on them. Set them a given distance (say 2 metres) apart on the vehicle before taking the photo. The actual distance doesn't matter as long as you know what it is.
Once the photos are imported into Sketchup and the scale set you can measure off any dimension or angle on the photo. It is quite easy to use and very accurate.
I don't have a vehicle to photo for you but I know of a very good one a couple of hours drive away. The owner may aggree to take the pics if you can't get them from anywhere else.
Best wishes for success with your project.
Regards, Terry