In the late sixties to mid-seventies, a couple of TWB-based Queenairs worked in PNG on an Army mapping contract doing laser camera runs at 35,000 feet. They were flying on 100% oxygen. IIRC, one of the crew suffered the bends in flight.
One of the crew - from memory - was Lang Kidby.
I spent lots of time in the RH seat of FWG and RUU.... some of it was even legitimate
The engines were not particularly fragile, they just needed to be managed appropriately. Don't overboost on T/O and don't backload on descent. This is much the same as the GTSIO 520 fitted to the C404 / 421; it is fine as long as it was managed right. Skytramps, when it was a GA company worth being in, ran a fleet of 10 Titans with an enviable engine record, because the CP (RA) educated the pilots in correct engine management and intelligent flight planning.
Queenair..... Nice!
(but better than a Kingair???? Oh pleeeeese
)