What kit are you planning on carrying? Before you order its worth looking at the ICU compatibility.
http://fstopgear.com/news/2015-10/f-stop-tips-tricks-icu-stacking-and-hatchbacking#.WII_6zZuDo4
There isn't much between the Ajna and Tilopa size wise. They are both a similar height. The extra 10 litres in Tilopa help the large Pro and XL Pro ICU's fit better but otherwise there isn't much in it. I wasn't so happy with the large pro or XL pro fitment in the Ajna, although they do fit I can see why F Stop don't recommend them as I felt they pushed into my back more than the large sloped ICU did and compared to them in the tilopa. The main difference between the Ajna and Tilopa is the harness, the Tilopa has more padding. The Tilopa is great if you are carrying a lot of kit. The heavier the kit you carry and the further you are planning to carry it the better the harness you need. If you are going use the large pro and XL pro then I feel the tilopa is a much better fit.
I'm tempted by the Lotus as a day bag and swap it with my Tilopa BC, the problem is I can't find a medium sloped ICU in UK stock any where and its pointless buying a F Stop bag without an ICU. I'm not sure I want to purchase from their european website after all the problems regarding shipping delays. I recently picked up the Sukha and tele master ICU to fit my long lens. Compared to the european website this combination is currently a bargain at Paramo UK. Its much bigger than I expected compared to the Tilopa BC i already have. For a Lotus I would need a medium sloped ICU but I'm not sure if the medium sloped ICU would fit a 70-200 f2.8 attached to a body. F Stop reckon its 25.4cm high internally and the camera and lens is 28cm long. I've seen photos with the canon 70-200mm f2.8 attached to a camera in the medium sloped so I think it would fit but its a big gamble. If anyone could confirm if it fits or has any idea why I could get a medium sloped ICU from it would be very appreciated.
Another thing I don't understand is why f stop don't do a medium pro ICU as its a big gap between small and large if you need the extra depth.