I've got an adjustable paddle and measured my preferred paddle length @ 27cm above my head.
I bought a new fixed paddle and made the mistake of consulting google for the best length, and recent pro opinion is to keep it shorter than 8" (http://www.ridingbumps.com/2013/08/25/the-new-rules-of-sup-paddle-length-determination/).

Keeping with my usual habit of messing things up, I figured I must be wrong and cut the length to 20cm above head (202cm total).
I went for a paddle yesterday and I'm pretty sure I cut it too short.

At present I only paddle leisurely with the Mrs on flat water.
With straight legs and very slight back bend paddling, the entry of the paddle is ~ 1/2 down the blade, and the exit is ~12cm from where to blade starts to expand.
My eye level is ~9cm (little lower than the image) above where the blade starts to expand. Sure I can bend over more, and can paddle short distances fine even with a paddle my own height, but my comfort point and getting the entire blade in seems to be around 30cm (11.8") above my head unless my technique is wrong and I should just get used to bending over more.
I have longer than regular arm length.

What do you folk reckon?