Mountain bikes and bike carriers question

mel.b

I'm going to be getting a mountain bike through the bike to work scheme. My main use will be to take the dog out with it, either with the walky dog attachment or bikejoring.

The biggest thing for me though is the ease that the bike will go on/fit onto a car carrier. I have a saris sentinel bike carrier https://www.saris.com/product/sentinel2 and I also have the saris bike beam that creates a 'top tube' https://www.saris.com/product/bike-beam. I have used the bike beam with my hybrid bike and it just doesn't fit the carrier well and I'm paranoid that it will fall off. So I want something a bit more stable.

I'm looking at a couple of bikes such as
http://www.360cycles.ie/mountain/1202-merida-matts-100-juliet-2017.html
https://www.cyclesuperstore.ie/shop/pc/viewPrd.asp?idproduct=100943
https://www.evanscycles.com/scott-contessa-720-2017-womens-mountain-bike-EV286242
But truthfully how it fits onto a bike rake will be the deciding factor.

Looking at both the merida and the scott, it doesn't seem like the bike beam would work as there's not enough space between the top tube and either the stem or the slanty bar underneath (sorry, don't know what that one is called )

The geometry of the Lapierre makes me think it will go easiest onto the carrier without needing the bike bar.

What are people's experiences of putting mountain bikes onto bike carriers. Does anyone have one on a Saris sentinel carrier? Does anyone know a shop that has a good range of mountain bikes in stock (ideally womens but that may be pushing it!) that would be happy for me to try putting it up onto the carrier?