jaka

Hi!
It all depends how light you build the model! Mine weights 3,6kg. 4kg is no problem for a pair of OS .26 four strokes turning good propellers

If you just put a model together,following the manual ...it will most of the time be heavy and this requires larger engines,l arger tanks and larger engine mounts....see the negative spiral.
If you on the other hand don't accept the manufactuers metods all the time and instead carv away balsa and plywood where it's not needed you get a ligthly built model that flies real good and scale like and not behaves like a pattern plane. But to always do this takes experience.

As I said before...anything bigger than OS .26 four strokes will be to much power and will make the model fly real bad! That's a fact!! Sorry! But that's my 32 years flying experince from flying pylon racing (still do)and buiding and constructing all kinds of R/C airplane models.
The opinion that one should be able to fly a twin on one engine in case of an emergence is is just not relevant !
You don't fly a scale twin on one engine! You land immediately if one engine fails!!!
Of course I can fly my DC-3 on one engine ...there is power to spare using those OS .26 engines (fuel 15% Motul Micro all syntetic oil and 5% nitro). But why risk it ??