Limit peak bitrate?

[oRBIT2002]

I'm trying to make Plex-friendly BD-rips of my collection but it was obviously not that easy. Plex requires <20Mbps videos or it will start to transcode and I don't want that so I need to keep bitrates below 20megabits..
My problem is bitrate spikes. Assume I set avg bitrate to 12Megabit. using the extra options I set "vbv-maxrate: 17000" and "vbv-bufsize: 34000" (according to different sources online...) My thought was that I won't get spikes above 17000 (17Megabits) but I still keep getting >20Megabit spikes anyway.
I'm no expert in Handbrake so I might've mixed something up. What am I doing wrong? Hints are appreciated..

[mduell]

maxrate=17000 bufsize=34000 means you won't see spikes over 17Mbps if you look at a period of 2 seconds. If you look at one second periods you could still have 25Mbps in one second and 9Mbps in the next.

What time period is whatever tool you're using measuring spikes over?

[oRBIT2002]

"Bitrate viewer". I think it detects the highest spike through the entire file when it scans...

[mduell]

Sounds like crapware. Over what time period?

[oRBIT2002]

I have no idea.
Are there any settings to disable spikes above a certain bitrate?

[BradleyS]

Activity log would help.

HandBrake's official presets limit 1080p to level 4.0. This should be sufficient, but you could change the level to 3.1 like the 720p presets for vbv 14000,14000.

[mduell]

I have no idea.
Are there any settings to disable spikes above a certain bitrate?

The vbv settings you mentioned can be used to disable spikes above a certain bitrate.

It's not possible to tell you what settings you need to use if you refuse to tell us what time period (tenth of a second, one second, ten seconds, etc) you're measuring spikes over.