You will get more noticeable 'popping' from the AIS system with one can rather than two simply because there is less silencing. Shortening an end can is relatively straightforward but again, it will be louder still and the 'popping' will be worse.

You can block the AIS system to minimise the backfiring if you don't like it. See here.

As for baffle packing/wadding, ebay is the best place to find it. There are loads of sellers, probaly some in your country, but here's one to get you going: http://www.ebay.co.uk/itm/Exhaust-Silencer-Muffler-Repacking-Kit

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