I skied early - mid 70's Long line until 6@36 then 15 off/36, 22/36, 28/36, and so on, Later in years you could skip75 and start @15off any speed. Rating system was different 3rd, 2nd, 1st class EP, Masters. and so on! Concave bottoms were in their child hood, as were non wooden skis.
Laying out a slalom course was a day long adventure of swimming and measuring this way and that way until tolerances were met. Nothing was piped together, Ropes with markings were stretched out from gate to ball and cross measured to next gate to measure.
Drivers used an analog speedo and a stop watch, ( which is why observer seats are 2 up) with mid course and end times so you didn't do a start at 28 finish at 40 to come out with a 34 mph time. The mid course time kept the speed almost consistent! Pull of a strong skier took some finesse on the throttle and steering. Ski Nautique, MasterCraft and Twin rig Hydrodines,were the top 3 until Supreme and American Skier came on the scene.
BTW my first end of season promo boat purchase was a 1978 MasterCraft with trailer for $6,800 +$60 for a cover.