+4 on the swinger is really going to make a difference on the jumps.
Having a longer wheelbase it makes it so much eaiser to set up the take off, and gives more control of the attitude in flight.
As to the spacers, my lad has been using them for a while for MX without any problems.
However one guy I spoke to, who had been using them for a long time, said that he had broken one, without any consequences.
If you do decide to use them, use plenty of thread lock on the bike studs.
Speaking from experience, they are a swine to remove if they loosen before the lug nut.