A 49-52mm step up ring fits tightly into the front of the stock fz5 adapter. The fit is quite tight as is but a more secure permanent solution would be to apply some silicon glue. One proviso - the 49mm threaded portion of the step ring interfers with gradual added extension of the fz5 lens housing as it zooms. The threads serve no purpose at all and should be removed- filed or grinded down or sawed off. If you're unable to do that, take it to a lock smith or hardware store and see it they can do it.
There is really no change in the stock adapter other than the plastic 55mm threads being replaced with 52mm metal threads.
Improvements over the now obsolete raynox rt5264p modification:
1) No extensive fz5 stock adapter plastic removal required.
2) The lens hood still connects.
3) Cheaper.
4) Less stressful.

Cons: None

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Fred
FZ5 & FZ1v2
http://www.ishots.net