kenkad, I don't have any sort of caliper, so don't have any way to get any accurate measurements. You are aware that the boom is aluminum and bends upwards at that point to follow the contour of the seat? Also, there is no rear disk brake mount on the Trike-X, so a different rear hub would be required.
But aside from the above, I don't understand why you would want to do all that work to install a mid-drive that doesn't "go through the gears", which is the number one reason mid-drives are becoming so popular. Of course I understand you could retain your front triple chain wheel and the motor would not become unsprung weight, but a suitable rear hub motor would give basically the same performance and the need for so many pedaling gears seems to be questionable once you have an electric assist installed.
Anyway, all the above is just my humble opinion and I support and endorse any choices you make since we all have different skills, capabilities, goals, etc. With the little 500W 48V Bafang crank drive my Trike-X will quickly accelerate to 20+ MPH in 5th gear using the thumb throttle override and will climb a 20% grade in 1st gear without over heating.
Good luck with your project.