Which hens to add to reduce roo damage?

I have a flock of 6 hens and 1 rooster, all different breeds, raised together from day-old chicks, who are now a bit over nine months old. This is my first flock. Two of the hens (a Golden Campine and a Brown Leghorn) are smaller than the others (not bantam, tho) and seem to be the Golden Laced Wyandotte rooster's favorites. Their poor backs are nearly naked from all his treading. I don't want to separate him from them as they free range and need his vigilance/protection.

I've just gotten saddles for them, but I also just read that the number of hens in the flock should be 10 per roo. If I add 4-5 more hens, should they be additional Campines and Leghorns? (My thinking is, if it's their size that attracts him, having multiple small hens will spread the mating pressure across more hens.) Unfortunately, they are the most skittish ones (REALLY hard to catch for health checks and on "the sky is falling!" end of the temperament spectrum), so if I enlarge the flock, I'd prefer to add more docile breeds, but there's no point in adding birds if it doesn't relieve the poor Campine and Leghorn. Another possibility is that their coloring is what attracts him, being somewhat similar to his breed.

So, how do I best help these two gals?: More small hens? More of his breed? Increase the flock size with whatever I want? Separate these two hens from the main flock?

 

Thank you. I hadn't considered the possibility they show damage more easily. Once weather permits, I'll have to spend some sustained time observing if he does favor them. One of them is tolerating the saddle completely. The other managed to get it off!