Since I have considerable experience with the Cardinal ARF, I would like to contribute to this thread.
I was visiting John when the first two prototype ARF Cardinals arrived from the factory in China.
One was slightly damaged, the other perfect.
We assembled the intact model and installed John's personal Brodak 40 (the FIRST Brodak 40) along with a four ounce non-uniflow tank, an 11-4 Top Flite wood prop and a two-inch plastic spinner. We positioned the leadouts by guess.
In that configuration, we made the first few flights. The prototype had no tip weight. As Brett correctly stated, it needed it badly. A few flights confirmed that 1 1/2 ounce was perfect.
Here are some particulars:
Weight: 45 ounces.
Balance point: 3 1/2 inches aft of leading edge edge at wing root (we DID NOT add tail weight)
Tip weight: 1 ½ ounces.
Front leadout: 1 3/4 back from leading edge. 2 3/8 inches spacing.
Rudder offset: Approximately ½ inch at rudder T/E.
Engine offset: zero.
We DID NOT round off the leading edge.
We DID NOT seal the hinge lines.
As we were quite pleased with the results, we gave the factory the go-ahead to start production.
At one of the Brodak Fly-Ins, they had an ARF stunt event. Four of us entered in the expert class. Gary Tultz, who had NEVER flown the plane, won first. I cannot remember the exact order but we all finished in the top five.
I loaned the plane to a fellow and he flew it to a first place in beginner stunt at KOI. He then splattered it and returned it to me in two shopping bags. I wrote a repair article while rebuilding the plane and published it -Stunt News, as I recall. After the repair, there were no detectable changes in flight characteristics. It gained less the one ounce.
I brought the plane to just about every event I attended, as well as trips to the local flying fields. I let anyone fly it and of course, solicited comments. For the most part, comments were positive. Besides myself, many people entered it in completion and it garnered quite a few trophies.
When it finally met its demise in 2008, it had around 600 flights, most of which were with the Brodak 40. I did experiment with a four-stroke engine, the OS Non-Surpass 40, and the results were quite good. At many of the Fly-Ins, we flew it at night, towing lights and having silly fun. Phil Spillman even killed a bat with it!
In closing, I should mention that I do not know if the factory made any changes from the prototype configuration, as they were told not to. There may have been some different materials used but I cannot confirm this. I have never flown another ARF Cardinal except for the prototype.
I hope this information is helpful.
Bob Z.