belts are a doddle to keep taut. just use belt tensioners :-) https://www.amazon.co.uk/Amazingdeal...belt+tensioner
They insure that all belts are the same tension all the time.
I have 2 on each of the delta's belts and I'll use them on the i3 as well.
Delta's don't taper at the top - where'd you get that ?

Only machine I can remember that did that was the little plastic cube micro things that came out a couple years back.
Where deltas rule among fdm is in speed and lack of vibration.
And small footprint for volume of print.
And easier to build.
lol

Planes are looking pretty cool :-)