That's interesting Rookie considering 'Berg/KTM 2T's are designed to run @ 60:1. I use Motul 800 in my Berg TE250 @60:1 and in my VMX'ers @40:1 without any issues whatsoever. A mate has just become the Oz importer for GRO (popular in Europe), so I'm about to give it a go. I too am not a fan of TTS. I had a customer many years ago who ran his Sea Doo XP (130hp) on cooking oil from the supermarket, never had an issue. He's a braver man than me in that respect!
On a different note with your Berg Rookie, I found the engine wasn't as strong as the Husky WR250 so I've done some playing: SX head, Suzuki NEDW needle on the third clip, 40 pilot, 165 main, red (soft) power valve spring with the dolly wound out flush to the housing. Electric smooth , pulls like a train, lugs beautifully & still has the berries when you want them.