I am installing a 165 track. On my 154 summit. Curious to see if there are any pictures. I am wondering about the rear tunnel. No one has any extensions yet.
I am going to see what it looks like with flap just strapped up. Off trail I could just get the rear flap remove kit. Bit I am worried about over heating on the trail. I will post some pictures of the 165 on the 154 chassis. When I get it installed.
One of my riding buddies stretched his G4 165" to a T3 174" track last year. No tunnel modification other then a trimmed snowflap, didn't have any temp issues.
You’ll be fine! Google the BRP Lynx sleds over in Sweden they just came out with their sleds with a short tunnel and longer track right from the factory. It’s the same tunnel as the Skidoo 850 also. Some of them have a “snow flap” thing connected to the rear bogeys.