To each their own. I've done three hardtop installs so far:
- No way would I want to sand off the insert art/shine with the playfield still in the cabinet, just from a sheer dust perspective (unless your pin is in your garage or driveway, and you don't care about dirtying up the rest of your cabinet interior). Also - how the hell are you supposed to get the factory stapled rails out of a Bally SS machine while it's still in the cabinet?
- I did my first hardtop by putting the playfield on a couple of sawhorses for the topside teardown, hardtop install, and topside repopulation. Then I got a rotisserie and used that for the next two hardtop installs. Hands down, way better/easier with rotisserie.
- I've done two installs where I just wet sanded the inserts and a third where I laid down a couple of light coats of rattle can clear on the inserts. No appreciable difference IMO and will probably just go the wet sand polished route for my next hardtop install.
- Clamps holding the hardtop in place during installation is a quick and easy no brainer. I do agree that one person can install it easily by himself (I did two that way) if everything goes right in the peeling back of the backing. However....if that peeling part doesn't go well and that backing rips or does something that requires you to use an Xacto knife or a pair of scissors to recover and get back on track, a second pair of hands really comes in handy. I make sure my son is within shouting distance when I start putting down the hardtop.
Bottom line: do what you're comfortable with after spending $300+ on the hardtop product and not having to buy another if you muck it up.