I built my first K-36 as soon as it was released. I had many good flights on it, including on opening days of the Great Mississippi Valley Fair. It even collected Iowa Gov. Robert Ray's signature when we met him in the Teen Tent, and we pushed for the adoption of NFPA codes. I always thought it flew best on 3 C6-3 motors, although it flew well enough on D13 and D12 motors. At some point it was in need of its second repainting and I decided to retire and replace it. My building skills had also improved considerably. It seemed disrespectful to throw out a flyable Saturn V, yet it was not good enough to keep as a display model or even to pass off to some young kid. It should die in battle as it were. It flew and recovered nicely with a D12-5. It took a D12-7 to produce the intended result, end even then the chutes deployed nicely at apogee, after the first bounce.
My second K-36 was built much nicer. The seams were filled and the scale balsa fins were finished with a hard epoxy surface. I modified it to fly with 4 additional B3 mini motors firing through the plastic F1 nozzles in scale location. The central motor was a D12, but the central motor mount was still removable, so I could have build an adapter for 29mm motors. I added nose weight to maintain the stock CG, compensating for the added weight in the aft end. It flew great on the five motors, and I never had a misfire. The K36 was a bit large for my taste; it would not fit in a box for transport with other rockets. On one trip I had the rocket carefully nestled between the back seat of a hatchback and massively heavy toll box. It was crushed in a minor car accident. In the intervening decades, I've made due with a Centuri Saturn 1B and it has flown well with C5-3, D12, and E20 motors.
Now I'm contemplating building my third Saturn V. I have a vintage Centuri, and two Estes 2157 kits. I'll probably buy a new 1969 as well. I know that I want to stick with the 5 motor cluster, even though I I have to fly it with with 4 A motors, A3 or A10s ( or vintage uncertified B motors), and true scale size fins, like the K36. Not that I trust catalog weights, but each new Saturn V kits seems to be getting heavier. A D12 and 4 A10s would likely suffice, but I have not run any sims yet. I should build a 2157, but I could be convinced to build a new 1969 instead.
Alan