Hmm, I did manage to find the 13/17mm larger size eheim disconnects for about $22 each, so $44 or so for a pair. I have them mounted mid-line. My Oase sits on the floor to the left of my stand (visible). It's not ideal, but it's also not an ugly piece of equipment. This makes maintenance on the prefilter much much easier.
Anyway, mine are mounted mid-line, just below the height of the glass. This lets me use about a 48" spring brush with no problem on both 'halves' of my filter lines. The eheim disconnects have a ridiculous center-brace in them negating the use of a spring brush from that end, but it's no big deal, I just disconnect half the eheim stop valve from the tubing for cleaning, then reconnect.