Excellent concept and a most-convincing build!  

Looked at Twin Otter pictures.  Smooth transition to single engine.  Appears to be stock build.  
There was a RW proposal for an 
Otter with tricycle gear. Back in the early 2000s, Beaver Aircraft Canada proposed new-build 
Otters in at least two variants. Their taildragger 
Turbo Otter concept looked pretty much like it any PT6 
Otter conversion. But the 
Super Otter was a different sort of beast. It would basically have been a 
Twin Otter with a Soloy Dual-Pac (twin PT6A-112s) in the nose driving contra-props.
I'm not sure what happened to BAC. Circa 2003, BAC bought Viking Air ... so perhaps BAC still exists somewhere within Viking's DNA?