I done a similar job on my 1299 base. Got a TTX shock from an R model, had it revalved and re-sprung by MCT in the UK. Very pleased with the work done. Also imported the Ohlins manually adjusted forks from a Pani R, had these resprung/revalved too, as most of my miles are not racetrack smooth! My bike tracks the surface really well on the roads I ride, and is a revelation compared to the stock suspension. Obs none of this was cheap, but money well spent for me. Hope this helps.
BTW, I'm only an average rider, but really notice when the sussies aren't up to scratch! Dave
