I currently own 2 Skylines - a 55-02 Deluxe and a JO-5 fretless. I just sold a 55-02 Deluxe fretless on eBay (to Malthumb).
I think the Skylines are fabulous basses, especially for the money. Are they as good as the USA models? Probably not, but they're darn close for significantly less money.
Over the years (I'm almost 50 - YIKES!), I've owned Fender, Guild, Ibanez, Rickenbacker, Alembic, Ken Smith, Sadowsky, Pedulla, Rob Allen, etc. Most recently, due to changes in economic conditions, I sold a Sadowsky Vintage 5 and a Rob Allen fretless 5 to get a pair of 55-02 Deluxes - and what I got for the Sadowsky was more than enough to pay for both 55-02s. The Skylines definitely do the job for me.
Are they heavier than USA models? I think a bit, but they are still comfortable and well balanced (and I have neck and shoulder problems - I sold my last Alembic for this reason).
As far as shielding, I don't know because I haven't looked. I've never gotten any hum from the 55-02, even when 18" away from my multitrack recorder. On the JO-5, there is some hum when that close, but this is due the single-coil pickups (turning away removes the hum). In any practical situation, I haven't had a hum problem with either bass.
As far as used Skylines, I agree with the comment that bass players commonly sell good stuff to get other stuff (GAS attacks!). I sold my absolutely wonderful 55-02 Deluxe fretless only because I wanted a JO-5 fretless more (and it's BLUE!).
If money was no object, I'd probably have USA models custom made to my liking, color, matching headstocks, etc. But that would be a luxury. But the Skylines get the job done.
Dan