Iirc, mounts in SWRPG need to be 1 Sil larger than their riders. I noticed that leonx mounts in Realms don't have the Sil 2 entry, so I assume they are Sil 1, just like their elven riders. I wonder if this was intentional or an oversight.

I can see three unique NPC mounts in the Lands of Terrinoth chapter and none of them are listed as Silhouette 2. Yet in the equipment section of chapter two all the mounts are Silhouette 2. So perhaps it’s just an oversight in the third chapter.

I must say though that I cannot find any rules anywhere in GCR or RoT about a minimum Silhouette for a mount, perhaps they choose to leave it up to the gm and players as to what makes sense.

I'd personally take a human on a horse to be s3 overall, but if you needed to be specific potentially s2 for height as the horse is a sort of s1 high s2 wide block with the s1 rider in the middle (inverted T). At times you'd need the cumulative s3 , othertimes the s1 specifically for the rider, s2 specifically for the horse. It makes sense that mount s is rider s + 1 if only for the fact it needs to support the rider's weight where the two are in balance with each other. Mount being smaller than rider would be very weird but could be a good comedy/ cartoony moment should that ever fit a session! Mount being much larger would probably be progressively harder to control/ride if it's not voluntarily in its rider's service.

Leonx are clearly bigger than their riders and I'd say they are s2 like a horse : https://www.fantasyflightgames.com/en/news/2017/6/12/focused-ferocity/

I'd also wondered for my campaign about ruling a way to link 'animal companion' p77 crb to 'riding' p63 crb for a mount owned by a character (characters who have their own horse or whatever, which is a story staple. Maybe with some realism, you can't ride your pet gerbil unless you're comparatively tiny, riding a huge dragon X times bigger might need a more creative solution, it's not quite going to work as a mount! Linking the talent to mount size could work well for my adventure- you need the talent to ride it effectively/ have the required minimal care/handling ability set. I needed to consider this as there could be some interesting rider/mount combos- I've also got NPC's riding strange beasts like bone horrors and carrion worms and need to cover the 'what if' of heroes wanting to have a go or stealing/ taking over such a mount!

Remember everyone has basic riding though- riding skill is only for more challenging activities, and survival can cover handling.

However (Mounted Combat RoT p83)

Once mounted, a rider and steed should be treated
as one character in most situations (attacks target the rider,
the steed does not act independently in structured encounters,
and both act when a player chooses an initiative slot for their
mounted character).

3 hours ago, Watercolour Dragon said:

I'd personally take a human on a horse to be s3 overall, but if you needed to be specific potentially s2 for height as the horse is a sort of s1 high s2 wide  block with the s1 rider in the middle (inverted T). At times you'd need the cumulative s3 , othertimes the s1 specifically for the rider, s2 specifically for the horse. It makes sense that mount s is rider s + 1 if only for the fact it needs to support the rider's weight where the two are in balance with each other. Mount being smaller than rider would be very weird but could be a good comedy/ cartoony moment should that ever fit a session! Mount being much larger would probably be progressively harder to control/ride if it's not voluntarily in its rider's service.

You might want to re-read page 109. Remember that silhouette is not linear, so silhouette 1 + silhouette 2 ≠ silhouette 3. A pickup truck and a single-engine aircraft are all silhouette 2, while a fighter jet and a tractor-trailer are silhouette 3. A rider and mount are not the same silhouette as a jet fighter!

3 hours ago, Watercolour Dragon said:

I'd also wondered for my campaign about ruling a way to link 'animal companion' p77 crb to 'riding' p63 crb for a mount owned by a character (characters who have their own horse or whatever, which is a story staple.

You don't need to have a talent to purchase a horse. The Animal Companion talent is more for a trusty sidekick than a mount. Think a D&D ranger and their trusty wolf companion, whereas a fighter just has a random warhorse. Granted it can be both, IE the paladin's special mount. But you don't need one to have the other.

'A rider and mount are not the same silhouette as a jet fighter! '

Funnily enough I did wonder that, have to admit I actually looked at jet fighter with pilot standing by it pics (I'm a geek I know) and also thought about the fact the rider of a horse say isn't much extra height when you consider the horse's neck and head and the fact the rider is seated. There's a bit more on p222 also. Choosing the closest to the relative size seems best- if the next size down seems too small and the next up too big (as with the jet fighter sized horse ) then you've probably hit the sweet spot! I was just too tired to update it/ think about it too much then.

The companion talent was just a suggestion for someone who wanted to make the steed both- like a pet they can ride, it's not needed to be steeded, nor is the rider skill if you're only doing basic riding of a simpler to ride animal, this ability is assumed as per the rules.