From a pure performance standpoint with the 308 round, it is not a big deal. Cheese, you have the velocities for the different barrel lengths for the 308 in the article I shared with you a couple of days ago. If we were talking about a 25-06 or 264mag, etc. we would have to look at it in a totally different way.
As someone just said, it is short as it is, as short as a 20" bolt gun. At 6' 1-2" tall & 280#, I figure the hardest part to get through a thicket is me, not the gun.
Here is something I would consider if I were you. Since the TC has no real action length, if you cut the tube to 20", you will be bringing the blast much closer to your face, so the blast & the noise will be more apparent to the shooter than a 308 would normally be.