Quoted from pinballizfun:
You stated you wouldn't be surprised if plastic fields became the norm. It was already tried, it failed. Both as a polybarb back-printed top slab over a substrate, very similar to a hardtop, but one that actually fits right since it was cut with the PF, to a full plastic field. Both were discontinued. Both were failures from the manufacturing aspect. It's not disputable that they stopped making them that way.
Haggis playfields are a combination of 9mm plywood & 4.5mm polycarb. That's what came in Celts & that is what Fathom Mermaid has installed. I love the playfield in my Celts & first impressions from the first Mermaid owner are very positive indeed.