I just got a ramp cracked in my STTNG, I was not able to find Ambroid Pro weld in my city and decided to try a alternative, Bondic.
The bonding liquid stays in liquid form until you shine UV light on it, it's supposed to be able to stay liquid for years without UV light, with UV light it hardens within seconds. The "weld" is clear with a slightly yellow tint to it. I have had good results so far, especially on clear plastics. You can build it in layers adding more and more as you go.
I also used Bondic on a couple of the subways below the playfield that had hairline cracks in them to hopefully prevent them from cracking more. I have also used it to fix one of my cracked plastics.
I made a small youtube video you can find below: