I have a s/a A10 and have situated the filter between the engine plates in place of the 'ski slope'. This is virtually in line with the return to the oil tank and, in my opinion, is a perfect place for this bike. I will probably have to disconnect it when changing filters, but this is no bother to me. Some have the filter higher in the toolbox, which is an excellent idea and is good cosmetically, but I actually have tools and a regulator in mine, so no room. Also, with the filter exposed, one may expect some additional oil cooling to take place.
Will post pictures when I can.