Ive been at it with the ramps for a year. If these hens who grew up playing on the ramp don't figure it out, I'm giving up.
Never had any issues with other breeds using ramps. Just these silkies. Did have some bachelor silkie boys I put in with the large fowl hens last year. Half of them huddled in a silkie pile to sleep. Others managed to fly up onto the roosts to smooze the big girls. Still have one boy in there as flock rooster. He's my amazing flying silkie because he can just barely manage to get the 3 feet to the roost with his girls.
Try a little bit of scratch leading up the ramp. That worked on my large fowl until they decided just flying up things was easier. In an enclosed space there won't be much flying.
On a note, I have netting over the large fowl pen more to keep birds in than hawks out. The ameraucana and easter eggers I have are quite capable of flying over the 6 foot fence. They free range a lot and I'm in the country so wings are left intact. In town you may have to cut the flight feathers on one wing to keep them in. It doesn't hurt them as long as the feathers are in the growth period. Like cutting nails. When they molt they will grow new feathers and it will have to be done again.