The hose clamp trick works on the waterboxer pretty well (try Home Depot).
Just be sure it is wide enough to cover all the rings and get German rings as
the oil ring is all one piece (not three pieces like the Brazilian oil ring
setup which stinks).
I have found that doing this proceedure when the engine is out is much easier
than with it in (putting the cylinders back on with the hose clamp took me a
day with the engine in or 15 mins with it out).
Have fun and when you get really frustrated, call Bob Donalds at
www.bostonengine.com and he'll send you out a rebuilt motor so you can get
back on the road :)

Thanks,
Ken Wilford
http://www.vanagain.com
John 3:16
Office (856)-765-1583
Shop (856)-327-0027
Fax   (856)-327-2242