Hi Adam L. Ooten,
We are currently preparing a KB article that shows how to implement a combined size validation on a target folder using RadAsyncUpload, the article is going to be released together with the upcoming Service Pack 2 release.
Apart from this, I've just tested your code and it works fine. You can find a link to a short video, showing it working, here
. What are the random errors that you get? Can you please screenshot it so that we can take a look.
Alternatively, you could try using RadAsyncUpload instead of RadUpload since the former provides out of the box client-side size validation. You can check it out in this demo.
the Telerik team