The BigMaxximum is only a 1/8 scale motor- 2300kv.
What you probably saw was the Bolido- looks the same as the BM but is much larger:
Bolido is 820kv. You could use the BM in a 1/5 scale I suppose, but only if it was very lightweight, like a stretched 1/8 scale ( Muggy or Savage stretched out to 1/5 scale for example ).
http://www.plettenberg-motoren.com/UK/daten.htm