Hello,

I'd say for Funtana 40 w/ 91 4-stroke, a 14x6 is best match. It will give enough thrust: 10+ lb., so you don't need additional thrust of a 15x4W. It will also spool up/down a lot quicker than an APC 15x4W.

I use Pro Zinger 15x4 on a fun fly on Saito 82. But I think Funtana could use a little more speed for the IMAC type moves. Besides, Funtana 40's stock landing gear is a little short for 15" props.