This question is for anyone who has installed an exhaust can onto the downpipes!

I'm swapping the bodged on aftermarket can on my 1999 CBR600FX / F4 for an original Honda exhaust. The aftermarket can slipped off with a little wiggling, but I can't get the Honda exhaust over the downpipe owing to the tight fit of the big graphite seal, even with the big band clamp removed!!

The original exhaust is 2nd hand and had the graphite seal inside it. Would it go any easier if I bought a new seal, pressed it onto the downpipe, then wiggled the exhaust over the new seal? Has anyone been through this before?