The hold doesn't have much height to it, so would be a struggle to get 2 full size bikes in it. We managed to get two kids bikes in the hold (with the handlebars turned round 90), but it was difficult to untangle them afterwards (!)
A compact tandem would just about fit onboard with the front wheel off, but you'd never get a full size tandem onboard, neither in the hold (I wonder if they've ever tried?).
Note that the disabled space is in between a partition and the back of some seats so space in the length direction is limited to exactly one-bike-length
Also, you (or the driver) need to be able to lift your bike up 3 steep steps to get onboard. I imagine an e-bike would be a challenge.
If putting bikes in the hold, there really needs to be something to tie them down, otherwise they just skid and bump about all over the place on the smooth floor, while lying on the pedals <scream emoji>
That said, it is a good service and we managed to get the whole family + 2 adult bikes + 2 kids bike to Kinross and back for a day trip (We did have to blag / be nice to the driver to get 4 bikes in though)