Would seem that there are many different versions then!!.Thunder is a big boy(His pedigree lines are Rajarani and CH Forstals),but according to breed standard he is too heavy.He weighs about 35 k,and is all muscle and incredibly strong.His legs are quite long,so maybe he would be good at pulling a heavy load ,at full steam ahead.!!.Don't know if he'd agree with me there!.He doesn't like wearing a back pack,let alone anything else.!!As for racing off,he just doesn't do that either!!.He is a good mouse catcher though,I'll give him that(has caught 3 to date!!).I think any urge to be a sled dog has long since left my Tundy boy,but who cares anyway,cos first and foremost,he's our beloved pet !!