Hi,
Unfortunitly, the U.S. is still stuck in the English system so I did some Metric unit conversions first.
[ul][*] Wingspan: 1000mm (39.4" )[*] Length: 820mm (32.4" )[*] Wing area: 30.65 Dm sq. (475 sq. in.)[*] Weight RTF: 1.4Kg (3.1lbs)
[/ul]
The key figure here is weight. I found no examples of what the "twynni svenson" looks like so i'll assume we want around 80 watts per pound.
80w * 3lbs = 240 watts for our motor power level
The [link=http://www.hobby-lobby.com/brushless-axi2820.htm]AXI 2820/10[/link] on either a 10-cell NiCd/NiMH pack or 3-cell Lithium would power this plane nicely.