Is that tube going to hang off of the action, or are you planning a BBL block. I wouldn't put a 1.5" anything on a 1.35" anything. The smallest action I would consider is the BAT round "M" action. I think it is 1.53". I have a BAT 10" x 2" model "L" action on my 1k HG....no BBL block. They go together like peas and carrots!!
If you are going with a bbl block, it won't matter .
Just my .02