| Others will have differing opinions, but I would not recommend adding links to a chain with soft links. If the chain is too short, I would get a new chain. Soft links are definitely NOT resuable. Taking a risk in this area in order to safe a few bob, will pale in comparison to having to replace crank cases that got ripped up by a broken chain.
As far as I know the larger diameter down pipes were not meant for the standard length swinging arm, and it's not too surprising that the wheel could interfere. Aside from fitting the longer swinging arm or a smaller diameter downpipe, the only possibility is to see if other tyre makes have a slightly smaller circumference. Are you running a 180 or 190 tyre? | 
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