I always claim the lane (i.e. move to the middle, like you) as I approach a roundabout. I started doing it years ago (before I had ever heard the phrase "claiming the lane") after a nasty attempted overtake by a car on one. I also avoid "filtering" to the front of the line at a roundabout. My reasoning is that once the bicycle lane disappears, it's single lane, so I shouldn't be overtaken but also I shouldn't overtake.
I've never had any problems from drivers for doing so. I don't why anyone would abuse you at a small roundabout, because they've got to slow down for the roundabout anyway.
You are right to be cautious when cycling through a roundabout. Australian roundabouts have been designed for vehicles, and differ from European roundabouts which are designed for safety. The other problem is Australian drivers, i.e. training and attitude towards cyclists.
There are many papers on this subject but here are some links I found quickly.
– Revolutionise roundabout design on bicycle routes, Bill Zhang, http://www.aitpm.com.au/ArticleDocuments/278/Bill%20Zhang%202015%20...
“Alarmingly, 41% of all cyclist-involved injury crashes at un-signalised intersections on local roads occurred at roundabouts, compared to 15% for other road users. 43% of all injury crashes at roundabouts on local roads involved cyclists (61% of injury crashes at roundabouts within inner suburbs).”
– High rate of crashes at roundabouts involving cyclists may be reduced with careful attention to conflict paths, Bob Cumming, http://acrs.org.au/files/arsrpe/Cumming%20-%20High%20rate%20of%20cr...
I go through 4 or 5 single lane roundabouts on the trip to work and generally behave as you do. The main judgment call is usually WHEN to claim the lane (rather than WHETHER to do so). I try to judge the speed and distance of the vehicle coming up behind to work out if they are going to get past me before we enter the roundabout. I'll slow down a little if I need to, but just as frequently I speed up because I know that I can get through the roundabout at a similar speed to the cars. If you claim the lane too soon and travelling too slowly, this can cause angst, but mostly it's smooth sailing for me. The trick is to be predictable and assertive (whilst having an escape plan if necessary). My main route includes Winston Ave / East Ave through Daw Park to Clarence Park, which is a 50kmh road.