The standard Yamaha set-up where the bolt is in double shear is definitely better, but plenty of things have shock bolts in single shear without drama.
If you were to do the long bolt in single shear thing, get a new high-tensile bolt and run it through both parts of the existing mount as well as the shock (in other words, don't try to mount it off just the outer part of the existing mount, because you WILL bend the mount and/or the bolt).