Since it has been a while, I guess another clarification is appropriate...
I have posted numerous times in the past but the most recent I found is HERE
No sense writing out the same thing again...... look at the link if interested.
Vno (Maximum structural cruise speed) is the engineering design factor for max HP decision.
An RV-9 with more than 160 HP can easily fly above Vno in level flight at max continous power (or less).
You may not think that operating within the yellow arc range is a big deal...... well it is.
If you use a bigger engine, and fully understand and avoid operating above Vno then you will probably never have a problem.
If you own an RV-9 with an engine bigger than 160 HP and still think that Vne is your limiting factor, you may some day have one........
One thing to keep in mind is that Vno is a indicated derived airspeed. So regardless what HP you have, as long as your INDICATED speed is in the green arc you should be fine. So at higher altitudes it is not likely to be an issue (as long as you TAS
remains below Vne). At lower altitudes, 180 HP engines at normal cruise power settings will easily push you above Vno.
The reason people get the idea that Van's doesn't like bigger engines is shown in this (and many other) threads.
If you incorrectly understand the issues related to using a bigger engine.... and spread that incorrect info to others, it clearly demonstrates the dangers involved with this sort of thing.
Please don't anyone follow up to this with "my wings haven't fallen off yet" (and get this thread derailed so that it gets closed).
Everyone can say that until it happens (God forbid) so it is not a valid response.
The important thing here in the forums is that correct
information be provided, so that people don't make serious decisions based on incorrect info and then have someone get hurt (or worse).