Use an Improved Cylinder, Not a Modified. You might end up getting away with it but it is not recommended.
I'd go with the Improved Cylinder and see what it can do at the range. If you do not like the performance check prices on the cantilevered rifled barrel for te 835.
Check out this page of the Mossberg link to see the barrels available from them. And I know there are some other complanies making aftermarket barrels for the 835 as well.

http://www.mossberg.com/products/access.asp?type=barrels&section=access

Good luck with the deer this year