Sekunda, when the covers came out I asked about it and was told they aren't fitted for the HXDA. Whether they'd work in a pinch, I guess you'd have to get measurements or try it out.
A very worthy alternative is the zip-around Studio Slips clamshell, that encases the entire amp, including the bottom of the amp. I had a couple that I used when transporting my Two-Rock heads between studios, and they were superb. Better protection than any slip-over cover, the only thing is that they don't work as easily as dust covers in, say, a studio because you have to lift the head up, etc, in order to put the cover on.
However, if you need a cover to transport an amp, best thing short of a road case.
Those D2F covers look well made, too!