Griffo me old.
Dunno who you've got in mind as clients but if they are weakened warriors
, I would think twice about the Robertson STOL. You and I know you should only use the "extra" performance as a buffer unless you have 'proper' STOL training.
It will only be a matter of time before some wannabe hero takes it to the edge of the STOL envelope and becomes a statistic.
Otherwise they are a fantastic performer, should be a tad faster than standard. Had a STOL P210 with all the fruit in stock for about 6 months couldn't bring myself to sell it.
The engine? take it for a good long blast at max cruise then get em checked. I'm personally not happy with the usual ground engine run test.
Airframe corrosion?? is not a respecter of inland or coastal conditions, if my memory serves me that era was plagued with filiform corrosion as a result of the painting method then being used. Either way the cost of a major adverse corrosion event may be more than the aircraft is worth. Its easy to check.
Good luck
