I do not have experience with that conversion to the P210, though I have been involved with other P210's with conversions. A factor in modifying any 210 is that in the case of inspection and possible repair to the wing spars, there may be no Cessna support. The result of this has been for a few of my clients, a rather costly airplane specific approval for either repair, or acceptance of a minor defect to the spars, because Cessna's repair data was not applicable to the modified airplane. This is not to say to not modify an airplane, but simply be aware that doing so can cause a disconnect with the airframe manufacturer, and you're on your own for technical support in the case of a repair.
In one case, inspection revealed that one of the screws which attached the wing to fuselage fairing had been replaced with a too long screw, and it had been bearing into the end of the lower forward spar lug. Approved data was required to do a repair (which could only be to polish the damage out). Cessna declined to assist in the required analysis, because the airplane was modified with spoilers. I had to hire a structures engineer to have the necessary analysis done, so an approval could be issued for my client. The damage visible in the photo was within a couple of thousandths of an inch deep of scrapping the center spar. Mods can certainly make a good plane better, but understand some of the behind the scenes factors...
