Good call on the Gas sealant.I used this on mine,
https://www.ebay.co.uk/itm/GRANVILLE...YAAMXQTQpR7xf0
Best I've ever used.Not silicone based though.
I had to chop some metal off the 30 Deg link pipe I had to use and from at end of my slip-on and make my own tightening slits with a hacksaw just enough so that when the clamps tighten they squeeze tight properly and then applied the seal to all the joints before clamping tight.
Also in the picture below you can see two metal bands front and rear on the Actual Slip-on(The ones with the Big Rivets).These flapped a little at certain revs as it's a cheap Chinese slip-on.I squeezed sealant under them spreading it in and under with my finger so when it set they couldn't move against the body of the Can.
As this sealant is water based it was easy to wipe off to make neat and clean with a wet microfiber cloth.
The car exhaust clamp was changed for a better proper smoother looking clamp like the ones on the short link pipe.