Ah, good with the extra weight!
Yes, the tires are not known to be great performers...
I couldn't resist a bit of numbercrunching.
From
http://www.ritchiespecs.com/specific...&modelid=91709
I get the scale as:
width 2464/(13*25.4)=7.5
length 8713/(43*25.4)=8
height 3131/(15*25.4)=8.2
So, let's go with 1:8.
Then the rule of thumb for the weight would mean we should be looking at a weight of very roughly (models tend to be lighter almost always) 14677kg/8^3=29kg
which would be about 65lbs!
Cheers
Jens