My mate fitted heated grips to my KTM RC8 yesterday (now winter is over!) and a sat nav power lead, which necessitated the leads being routed under the petrol tank. He is a trained KTM mechanic and said that it was best to remove the tank BUT they tend to swell due to the additives in petrol, and they can be a right bastard to remove and refit.
He wasn't wrong as it had to be removed and refitted with the assistance from a long pry bar. Had to remove the rubber inserts from around the front fittings to get it to bolt up, as the tank swelling meant that the holes for the bolts were about 5mm further forward now.
So if your bike has a plastic tank, beware of swelling.
Is your mate Jerry from Jim Aims (used to be known as Jims joke shop around Hedingham years ago)? If so, hes a really decent bloke.
Always more than fair when he MOT,d my bikes.