Hi Methy,
no problems with stink eye thus far, i stick to my own advice - if fewer people see it your chances of running into trouble are greatly reduced, i always run respectably meaning if people are around i don't power up, if i come across walkers particularly with dogs i scrub all speed, stop if i have to, always give them priority on single track etc, its always greated with a "thanks" or an "evening/morning".
If your going to romp around regardless of who's about sooner or later the real law will be onto you, they'll apply pocket bike law and you'll be shagged
I've only had one small incident from a horserider - i'd pulled over to the side of the bridleway/fireroad to not spook the horses and the riders (2 women) stopped next to me, "is that a motor?" she quizzed with a pissy look on her face, "regenerative electricity" i replied (slight lie but meh) , her look changed and she rode on appeased that i wasn't gassing in the forest didn't seem to worry the bike was powered i guess because it is fairly green. This was when i had two massive lipo's sticking out the side of the frame and a hub mind, the bike is a lot more stealth now to look at although louder when powered.
I do get strange looks from the MTB'ers mainly, i think that when you pass another cyclist it's natural curiosity to see what they're riding, guaranteed once i pass them they will either stop or slow right down for a better look, no one has actually said anything yet they just want to have another look, again bear in mind that i dont power past them, im either freewheeling or giving it some pedal assist, again this pisses no one off so theres no problem.
In my opinion it would only take one or two reports to the local police to cause me an issue so my approach is this:
ride at the right time, early morning, just before dark.
Be courteous to all other users, even if they are objectionable a polite response normally leads to exchange of info, telling them to f off will get their back up and likely result in a report to the police.
if i do all this, and i do, then everything is always fine, of course once we get to the police stage (if ever) i will argue my bike is legal and if the current setting is minimal, it is!!! but i think that stage is best avoided to begin with - prevention is better than cure and all that.
i know what you mean about feeling like a criminal, its sad really, we all know the unjustness of it all, its not like we are selling crack or any of the other crap that goes on in this world.... BUT at the end of the day we are all running "illegal" rigs so i believe my approach is the right one, if you don't want any problems at least make the effort to not cause your own.
this is mostly why i dont wear a helmet also, less safe unyet safer
Cheers,
D