Pure Cannabis extract - Yield?

For those of you making pure cannabis extract (RSO), what is your average oil yield per oz of material? I have tried several methods and I am getting around 2.5 grams oil per ounce of material.
Tried the following:
99% ISO - Room temperature extraction - Rice Cooker evaporation
Everclear - Frozen extraction - Double boiler evaporation
Everclear - Heated extraction - Double boiler evaporation

All of them yielded around the same. Am I on the right track or am I missing something somewhere?

Thanks

That's a tad less than 10%.
And it's what I get from trim.

However, after talking to gray wolf, and seeing his yield.
I started using frosty buds and a secondary extraction.

My best yield to date is 22% by weight.
It's not as clean looking as the gentler extraction, but every bit as effective on skin growths.

Google "Gray Wolf", and "terpinator."
All will be revealed. :D

Aloha,
Weezard