Keep an eye on your chain tensioner idler bolt!

[NYTurbo]

21/41 is border line a good gear combo in my mind, significant dog leg . As per chains Hurricane usually has plenty in stock

 

[Turboflash]

Chains have a finite life. Shorter on sleds with big tunes and lots of traction. Just laws of physics - more load = more stretch.
Someone should invent a "heavy duty"/performance chain. Better metal (chrome moly , tool steel, fatigue-proof, etc) for a stronger/longer life chain, especially for 300+ HP. Drag racers would want that too.