Nifty idea! I've thought about building a 110-120% Tipo and using an OS120....
Yours would be awesome! The Tipo has such nice lines, good to see that styling alive and well.
Just an fyi, for the os160, if ground clearance for the prop becomes an issue, many pilots use an apc 3 blade prop (15" diameter, I believe) that is re-pitched by Dave Lockhart.
You may also be able to extend the gear legs without ill effect by using carbon fiber struts in place of the original ones...MTK has posted on that topic before.
If you do build it, post some photos for us!