Nice work Kieran. It will be interesting to see how those Mitaka pistons go, as you say plenty of other people use them so cant see why they shouldnt be okay.

If you are worried about your crank seals you need to carry out a leak down test, this will confirm whether or not they are leaking. If you do a search there is a recent threard on here about how to make a kit and carry out the test.

Stripping the bottom end is a very straight forward job on these bikes, if you have managed to take your engine out and strip and rebuild the top ends it shouldnt be a problem for you.

If the centre seal has gone then you are looking at a crank rebuild which isnt as big a problem as it used to be, genuine main bearings are available still if you know the right people and I recently bought a new mc16 centre seal from another forum member who bought a batch from Japan. It was his last one but hopefully he should be able to point you in the right direction if it turns out you need one.