What's a good discharge current for a LiPo battery without a C rating?
I found some data here:

http://www.globalmarket.com/product-info/606090-lithium-polymer-battery-3-7v-400mah-for-smart-watch-10924302.html

strangely the item listed there is not a 606090, but a smaller 592627
but the C ratio will be the same.

this may not be your exact cell but should be representative.

0.5C continuous, 1C peak