24 for me, seems like a good compromise, longer than a 22 and the total length is noticeably less than a bolt gun.
I get 225 Sierras going 2600fps with RE15 out of a 24 inch Addams and Bennett Savage, If I wanted more, I would add more powder. I dont particularly think the 26" is needed to make the 35 Whelen and effective powerhouse. Either way, Im glad to see Rem take a responsible approach to reintroducing this round to the HR. Hopefully, being the name on both the gun, most brass, and much of the factory ammo will help bring everything together successfully.