Dave at Rowan Engineering has been back on to me and the slight bracket mod is already in hand. I can confirm that they WILL be offering it in both left and right handed options for those of you who use sidewheel scopes. From what he tells me the 'lefty' version of the S400 model is the more popular of the two anyway for various reasons.
When they first manufactured these it was .177 calibre only but bowed to public demand and produced the .22 version. Whether they will produce a .20 and .25 version, I suppose will down to demand, as the gun isn't made as a standard in those calibres. I have to restest the new modified bracket when it arrives but it's a forgone conclusion it will be OK and then I suppose it's all systems go.
I am one very happy bunny at the moment, being the only person with one of these QB mags. That situation certainly isn't going to last long!

Steve