Slight thread mine, however I thought it may interest some to know my engineer has told me in writing that an ADR 3/02 seat is fine, provided there is 800mm height from seat cushion to top of head rest without the head rest being 'excessively' extended, and suggested a 50mm gap max. And if he's happy to sign off on that, I'm happy to build to it
That is for Queensland rego, if it matters.
Headrest may not be an issue for me anyway because I'm looking at a fixed headrest seat - they are easy to come by and can look ok.