Absolutely, it has a profound affect on my data. Doesn't have anything to do with accuracy. But it would affect the data set as a whole. As I've mentioned, my test simulated installing the transmission in a car with basically infinite weight... An impossibly bad scenario. The transmission is also not bolted to an engine block... Since Subaru added 4 bellhousing bolt locations in 1998, I'm sure the engine provides substantial support to the case assembly as a whole.
There are tons of shortcomings in the design of this particular test as far as real-world conditions are concerned, I'll admit that. Though the idea behind this study of the case was as a proof of concept, and primarily to see where the weaknesses are. Since I was interested in designing a reinforcement when I started this project, I wanted to know at which locations I should apply reinforcement rather that just blindly bolting chunks of steel here and there. I was also very interested in being able to test the 5mt without the reinforcement as a baseline, and then see if there were any improvements with the reinforcement installed. This was purely a relative data comparison, I didn't really need to find exact figures against a set point away from the transmission under real-world driving conditions with a particularly high precision... Just basically needed to answer 3 questions. Does it flex? Where? And does the reinforcement help?
Any way you look at it though, smoothly applying 230ft./lbs. of continuous torque to the input shaft, even with the output shafts completely bound up is probably nothing close to the kind of force the transmission sees if you drop the clutch from a high rpm with the car at a stop.
In addition to my own business, I work for a truck body manufacturer as a Quality Manager. But most of the projects that I've directly worked on at this job have involved tooling for the production line. Factory workers beat the crap out of tools, fixtures, etc, so we have to find ways to make sure that they stay together for years under daily abuse. I do a lot of work with our warranty dept., so I document and give advice on parts failures that I have inspected in the field as well.