"STC costs, you need modifications to both firewalls, exhausts, mounts etc. I've heard it's about $100K mod on top of the STC, which is about $120K. That's why the Super 5 mod is something that's looking quite attractive. Only $60K aside and it gives you 80-90% of the performance of the -10's. But of course, then you're still on the 5400hr schedule, which the -10's don't have to follow."
I disagree. I bought a plane with the Super 5 conversion (FYI there are only two flying and I am one of them). Before I bought the plane I spoke directly with National Flight (the holder of the STC). They told me they are exactly the same but Honeywell will not allow them to do the conversion anymore because they do not collect royalties on Super 5 conversions. What was interesting is that even thought they are the same, the STC on the Super 5 has a higher EGT limitation So in theory the Super 5 produces more power, but at cost.
Neil Rosoff