AMP ads for google adsense loading very slow

Lately (in Oct 2016) we have enabled amp-ads for google adsense on few of our sites. But we are continuously observing very slow ad load times and this has impacted our adsense revenue.

To put things in perspective, we have added amp pages (accelerated mobile pages) for some of our sites in july-august 2016. Since then, we have observed a steady increase in our amp traffic. Performance wise, we have been very happy with amp pages as they load very fast on slow mobile data connections.

But things have been bad since we enabled google adsense on these pages using amp-ad component as specified by google. Typically adsense ads appear 3-4 secs after the page has been loaded and by then the user has scrolled down the page. Apart from the loss of adsense revenue, it is also bad from usability perspective - as the user sees a big empty space at the location of ad. (Please note this is also true even when the page is served by google cache)

I have tried searching on net for a solution for this, but in vain. Only interesting discussion about this is part of AMP A4A initiative (AMP Ads for AMP Pages) which explains the cause of delay as the time taken for rendering cross domain iframes. The corresponding blog entry is here which explains how new A4A initiative fixes this delay. But somehow this fix does not seem to be yet available for general public.

We are waiting for AMP A4A support for adsense. If some of you know about its general availability, do let us know.