RatherbeFlying
Your comparison with the Chinook does not end up as 'basically the same problem'. The Chinook has both engines at the rear, so there is no shock-loading on the long driveshaft in the event of an engine failure. The Belvedere had a similar arrangement to the tilt-rotor, in that the shaft was a 'synchronisation' shaft, with an engine at each end of the aircraft, but if one of the donkeys took a break, then the shaft normally did too.