Hi Mike, Personally I am yet to see or hear a twin set up with 2 synced turbines that 'sounds' any better than a single turbine anyway... the bifurcated pipe roar with a single turbine set up sounds great to me!!! defenitely a better sound than even two snyced turbines in my opinion. If you can hear a difference the engines are 'not' synced. One way to really make a twin install sound great is to set one engines idle slightly lower ie 500 rpm, as no difference in residual thrust will be noticed at lower idle rpm's anyway! and they then will sound waaaay!!!!!!! better acoustically when on the ground taxiing etc If indeed snyced correctly you likely will notice little sound difference at all!! IMHO

The redundancy question of having two systems is also a mute point for me personally as far as I can see as you need twice the ECU's fuels systems UATs etc etc... more to fail! I would just install one 'well proven' 100% reliable quality turbine along with systems.... that said I have always fancied a large Me 262 or Learjet oneday but thats a different scenario altogether

Cheers