You will be fine running 20% but you will probably have to retune your vehicle. Generally speaking 20% has a higher oil content than 30% which will cause your engine to run at hotter temperatures.
So go ahead and use 20% but retune it for performance and make sure your temp isnt too high. I dont tune my engines by temp but I also dont like them to run too hot. For me I like to keep it at 270 degrees or less but will run as high as 290 if its blowing plenty of smoke through the whole rpm curve. Any more than that and I richen it up to cool it a bit.
Hope this helps.