I am wondering if I need to use an internal reinforcement cylinder inside of
a section of steel square tubing. The square tubing in question is 2.5",
with a wall thickness of 3/16". The fastener will be a 9/16" Grade 8 bolt,
with a through hole of 5/8".

I will also have a 1/4" section of plate outside of each side of the steel
square tubing, with a width spanning the full distance of the flat side of
the square tubing, from shoulder to shoulder (about 1.75" x 1.75").

Will I need to insert a piece of pipe inside of the steel square tubing to
keep it from collapsing, or will the 1/4" plate on the outsides spread the
load sufficiently?

Thanks for any thoughts on this.

Jon