I always plan my IFR trips to fly in VMC on top. There’s plenty of info on this subject on EuroGA, how to determinate the cloud tops, etc.
If VMC on Top is not possible, I look at the option to fly in IMC below freezing level. This works very well in my part of the world, where there is hardly any terrain around. For example: Malmo ESMS to Lelystad EHLE can be flown at FL040.
These two strategies work very well with a small aircraft without icing protection. I do have weather data onboard (ADL120) to make sure I stay away from nasty weather.
I sometimes read that people use a third strategy, which is: Cross weather in IMC at a high altitude where the temps are so cold that the icing risk is minimal. But this introduces new risks, like fuel sensor icing and air filter icing. Also, in case of an emergency, the escape into warm air is a long way down.
And one can’t really be certain that there is no ice. I remember from the IR theory that ice can form in temperatures down to -30 degrees Celcius.
Why would one prefer the strategy to fly through weather at a high level (say FL200) when one could also cross it at a lower level in warm air?
1. in many parts of Europe, IFR MEAs are FL100 or even FL150, which often does not allow the FL40 option (unless the country allows IFR OCAS, but that’s more tedious thing than flying airways)
2. in winter, the freezing level may be at or close to the ground, so even if the MEA is FL40, that is no option
3. flying FL200 instead of FL40 could be worthwhile performance-wise (especially if you have a Turbo
But I agree, being up there at FL200 with a non-FIKI aircraft, with lots of icing conditions below, is a risky business.
My SR22 is limited to FL175 (but could climb to FL200), but I found out that 160 is really the highest where i feel (very) comfortable. But I will not fly above 130 if I had no chance to descend to 130 without icing. FL250 like many fly in SR22 turbos actually scares me, ad I would not want to take the kids up there in a non-pressurized A/C
4. You could fly into a CB…
being up there at FL200 with a non-FIKI aircraft, with lots of icing conditions below, is a risky business.
What are the risks?
Did you forget to add the 
?
Descending through IMC is usually not a big risk, provided you know you can descent all the way down to a landing or positive temperatures. Descending from e.g. FL160 with moderate icing to FL120 with severe icing which is also MSA would be bad.
My standard cruising level is FL150 (turbo: the higher the more MPG) but I have no problem going to FL200 and do so when required by the weather. The MH cannulas work very well up there, the aircraft handles fine and I feel comfortable — unless in winter when it can get cold.
Peter can only use the cannulas (legally) up to FL 180 with his N-reg.
Very few FAA inspectors at FL180 
Under EASA there is no such restriction luckily.
achimha wrote:
Very few FAA inspectors at FL180 Under EASA there is no such restriction luckily.
Whilst that may be true … as with just about any other regulation, and not restricted to aviation, there is NO problem until there IS a problem and now you have a much BIGGER problem.
In the example cited above, if one were to make some stupid mistake, say hypoxia induced after a couple of hours cruising around in the FLs, and there was a welcoming committee at the airport site or investigators at the crash site, then quite likely evidence of equipment on-board, or lack thereof, would be established.
I also think that Peter is one of few, who take a TB 20 up >FL180 on a regular basis. Cannulas work well even at FL250, even though FAA doesn’t believe it.
