I'm part of this year's intake at Cranfield in the UK studying aircraft design, and we're looking an 8 seat tiltrotor aimed at the corporate, SAR and offshore rig market.
It's at the early stages of design, but the number one risk of the project is mass, and keeping it low enough to achieve a sensible payload. With an AUW of 7500kg, we have a payload of 2500kg. Not great when compared to some of the pure helicopters in that range!
Range of 750nm, ceiling of 25,000 feet and cruise of mach 0.55.
Big problem is as you say the extra stuff required for two engines hung on the wingtips, with the OEI shaft and linkages. It's very unlikely we'll meet the EASA requirements for climb under OEI conditions - as I understand it, the Bell609 isn't capable yet either.
Your project looks very interesting in comparison!
Are you looking to certify in CS 25 and CS 29? One of our problems is that a tiltrotor doesn't fit anywhere, so we spend hours trawling the documents for gotcha's!
How big will the final aircraft be (I see a figure of 9,400lbs - is this the final plan or will you go bigger once the concept is proven)?
Does there need to be a pilot at all, and if so, does he really need to be sitting where he can see the load, but have to suffer a swiveling cockpit and the fear of rotorbust, when perhaps he could sit further back out the way and let CCTV be his eyes?
Can you land in conventional aircraft mode, or does it have to be helicopter?
I'm sure there will be many more questions after I've read the info fully!
Best of luck.
Glum.