I have a Carlson's .705" that fits the 835/935. I only fired a few rounds through it, 2.25oz #4's weren't bad at all and it threw a very even 171 - 10" and 321 - 20" in 45 degree weather with 3.5-2.25oz-#6 Hevi13.
The Ventilator is probably awesome with 6's or 7's but I just can't get away from my old Kicks in the 870.
$20 shipped for the Carlson's
$20 shipped for the Ventilator