http://www.fai.org/record-aeromodell...spacemodelling

The FAI website is a bit convoluted but if you choose "F3 Open- Radio Controlled Flight" and leave the other selector as "Choose...." it gives you all the current records and current claims pending approval.

Piston engine speed is listed at 405.30 kph. That's a "mere" 253 mph. So the dynamic model soaring scene has already moved WAY past what a piston engine model can provide.

There is no classes for electric power speed near as I can tell. Just one time for a closed course F5D racer.