Barrel clearance around the SIDES of the heat riser???

Hi,
 In my prototype build the heat riser is firebrick, there is overhang to get the correct dimension (5.5 x 5.5).  The diagonal distance of the furthest corners is 17".  The ID of the barrel is 22", which leaves 5" BUT
I still need to add in my 1" refractory blanket, plus the mesh to hold it on.  That is going to be a tight fit.  Is this normal?  I have read about proper distance of barrel at top of heat riser, but not at the sides.
If it is too tight, does that mean I need to trim ALL of the bricks??

Thank you!!!

2 inch per side barrel gap is fine. I would say.

But you can check

https://www.google.fr/search?hl=en&dcr=0&ei=QOEgWpSAMonfgAaK7pAY&q=%22barrel+gap%22++site%3Dhttps%3A%2F%2Fpermies.com&oq=%22barrel+gap%22++site%3Dhttps%3A%2F%2Fpermies.com&gs_l=psy-ab.12...708962.724336.0.727827.20.20.0.0.0.0.112.1843.17j3.20.0....0...1c.1.64.psy-ab..0.18.1632...0j46j0i46k1j0i67k1j0i46i67k1j46i67k1j0i22i30k1j0i22i10i30k1j0i7i30k1j0i30k1j0i8i30k1j33i22i29i30k1j33i21k1j33i160k1.0.6uKq7W685_8