From what I could see from some pics of exposed cams, the inner valve buckets don't have enough clearence with the cam bearing towers to get on them for valve spring compressing (without moving the cams somewhat).
When VW went to SOHC water pumpers in 1974 (Dasher) and 1975 (Rabbit), they used a "shim plucker" tool that resembled snap ring pliers with 45* angle tongs, to pluck out the shims from the depressed buckets. What holds the sims so tightly into the buckets is the oil film.
Thankfully, these Hinckley twins don't need very much valve adjustment, if any. My educated guess is that if anything, the valve clearences should tighten slightly as valves recede. (Valve recession is the sinking of the valve into the head as the valve face and cyl. head seat wear.)
