No, this buffer tube is larger than the manufacturer's stated maximum diameter.
YES- - I do not know why the "expert" said no.... I purchased this for use with my tailhook mod 1 and it works great. I do wish it were a little shorter, but it fits the diameter of the tailhook perfectly.
I will second Charlie from Florida's answer. This tube works great with the Tailhook mod 1. Tailhooks can be spread a bit for installation, but I didn't need to with this tube. Just for FYI's sake the SB Tactical SB-Mini fits good also, but doesn't lock on like Tailhook. With braces like the Tailhook you can also slide forward to change the "Pull" length the ATF will be looking for if they end up using they're pistol brace/sbr scoring chart. SB-Mini will add 1.5"s to "Pull" length, unless you drill/grind out step. Currently have Tailhook mod1 on this buffer, had SB-Mini before this buffer beforehand.