mouthpiece of Ithaka sits on the first step Tax. That is 1mm after the top of the base. So mouthpiece goes deep down to the base for 1mm only and it stops. Because the first step has a diameter of 15,8mm and the mouthpiece a diameter of 16mm. I cant understand from where it leaks.
We can eliminate of course the steps on Ithaka's base and make it exactly like Tilemahos base because:
1. The basic feeding doesnt need a stop.
2. The new rebuildable part doesnt need a stop too.
So yes, eliminating the steps is ok. The only that is needed maybe is a little fatter o-ring on the new rebuildable part of Ithaka. O-ring now is at 2mm width and we may need an o-ring at 2,5mm width. That way we will avoid the first o-ring to pass on the other side of the wider hole on the GGTS base (because the bottom hole of GGTS base will be at 6,5mm and not at 5mm that is now)