If you’re on about the gen 2 Galaxy from 2006 to 2014 (the gen 1 being that effort that was shared between the VW Sharran and the Seat Alhambra) then it and the SMax (SMax was introduced at this stage) were both based on the Mondeo estate chassis/floor pan and essentially the same car, but for the taller headroom in the rear of the Galaxy as the 6th and 7th seat were designed for adults to sit in so their knees were not up by their ears as they were in the SMax were the roofline tapers down a bit from the middle seats (headroom for the middle seats was the same in both cars). But in terms of length the Galaxy exterior dimensions is only about 52mm longer than the SMax (4,820mm vs 4,768mm), so interior dimensions was essentially the same in terms of length and width. Obviously the volume was greater in the Galaxy but it was all additional volume due to the higher rear roofline, so not really usable additional volume, other than for additional headroom for occupants of the 6th and 7th seats. To use all three of the middle row of seats you’d have had to remove rear wheels and put the frames in at an angle or something like that.
They might have grown the Galaxy in later generations, I don’t know, but certainly back when I was comparing the two models in 2009, they were essentially the same apart from the differences mentioned above, so not going to be a huge help in terms of fitting MTB’s in there.
Looking at the photo of the bikes in my SMax above (two long travel 29ers, medium frames), you could have squeezed the two bikes closer side by side and utilised one of the three middle seats, but you’d struggle to have squeezed them any closer enough to liberate the middle seat and fit in two adults in the back. However thinking about it, if you squeezed the bikes in closer together you might have been able to utilise one of the middle seats and one of the third row seats. Never tried it so can’t confirm and not sure where you’d put the rest of the gear like wheels and boxes.
