That is nice little prop chart-
when I built the the models with the ZDZ40's ("pizza boy's and mine) The object was to simply prove out the first phase of doing a "pattern legal gasser."
In that none of the other small gassers of the time seemed well suited-we use the ZDZ40- rear intake -rear exhaust - very compact.
The power available was already a known - so we simply designed structure that would match the reqd 5 KG all up weight.
The resultant models worked very well - tho some thought they were grossly overpowered (like being too rich- easy to fix)
No attempt was made at making a copy of the copies of copies of models already available for pattern.
The large displacement gasoline engine (if it is all done right) is perfect for this event.
The engines will run well and produce plenty of power- at reduced power settings
This reduces wear n tear and offers a power RESERVE which - on many occasions , really maintains a constant speed and smoothness of flight.
If you fly WOT all the time - this ain't for you.
Also, the power impulses of a two stroke are double those of the four stroke - so less "BANG" on each power pulse.
Been there -- probably had over 30-40 competition four strokers - they do work but you can't fool mother nature.
The props DO slow down between each and every power stroke .
best setup in an IC engine (single cyl) is a BIG displacement - fairly low compression two stroke ---with a electronically timed spark set to as retarded as possible for all but full power applications.
This reduces that "bump" common to all of the glow engines which fire on compression.
Using gasoline allows the use of lower compression - SO----------
Power which can be produced will never equal a same size setup on alky and nitro - That is a given.
But the total compromise of the bigger slower turning gasser -- with properly timed firing - is very good.