Help converting drive system on a solid shaft shallow-V mono to flex cable

[sciesielka]

As you can see in the photos attached, the Playtron Candy has a 'straight shaft inboard engine' style setup. It's over 30 years old, but still looks and runs like it did when it was new in 1987. It's lots of fun, but after finally upgrading the electronics this year (2019), it became apparent that it can really use some further work. It runs on a 20-turn 540 brushed motor and 60A ESC now. The boat is 20.5" long by 7.6" wide and weighs a little over 2 lbs with a 6-cell NiMh battery.

Here is a video that shows the way it ran originally as well as how it ran with the various changes I made to it recently. I also have stick-on trim tabs that I've tried and they don't help with the porpoising, or it slows the boat down way too much!

My question is, without removing the stuffing tube and the section of the hull holding the stuffing tube, can I put a strut and flex cable on this boat? There would be a sizeable gap between the stuffing tube and where the strut would start. I can't get a larger diameter stuffing tube in, so I won't be able to use a Teflon liner. Also, would the bend angle from the stuffing tube to a strut be too great?

This is my anticipated shopping list, minus couplers, water cooling and misc. parts if I can make the conversion:
ose-cable-098L : OSE assembled .098 flex cable with 1/8" prop shaft, drive dog, bullet nut and Teflon liner. According to OSE, this will work in a 5/32" stuffing tube without the Teflon liner.
ose-80046 : Micro Strut. Strut bushing is made for 1/8" prop shafts.
ose-80052 : Rudder with water pickup

Thank you all for your help!