Oca and Ulluco crop

Planted Oca and Ulluco in the spring having been inspired by Simon Hickmotts 'Growing Unusual Vegetables' book to try something different.
I started them off in the greenhouse in pots and then planted them out in April in a deep bed that was treated with lots of lovely well rotted manure.
The Oca grew quite well and the top growth spread over onto the next bed. The Ulluco is clearly irrestistable to slugs and must have fed a whole new generation of the b******s for next year.

The results? Well the Oca was not bad - maybe got back 5lbs from 10 tubers. The Ulluco was very poor - from 10 tubers got back 20 but they were small/tiny. The Ulluco did produce lots of tiny tubers from side branches that touched the ground - but nothing worth collecting.

Apparently you need a long warm autumn to get good results - so until I get a poly-tunnel I don't think I will grow them again.
Anyone else tried these two?