I have Dorkings myself and they are pretty good flyers. They wouldn't have any trouble with a 3' door. My nest boxes are about 3' off the ground and my Dorking lay in them just fine. My Dorkings also roost almost 6' off the ground.
I have a couple of Wyandotte roosters that free range. They have some size to them now, but they still sleep in the rafters of our barn. So I suppose they don't have issues flying either. LOL. Our rafters are probably 8-10'. They sleep up there with our Black Giant rooster.
The silkies need ramps for just about anything. They just don't get any lift with those feathers of their's.
Oh yeah, my hens make their daily 3' jump/flight with their wings clipped. I thought that would slow them down when I was trying to keep them in an uncovered enclosure.. Boy, was I wrong. LOL
Mediterranean, light breeds are great flyers. I had White-faced black Spanish, La Fleche, and Andalusians and they would all go way up in the trees. The La Fleche and Spanish especially.
. This is what I have and they all fly to at least 5 feet off of the ground to get to my roost in the coop. RIR's, Black Sex Link, Phoenix's, Silver Laced Polish(which is on my avatar), and a White Leghorn. Sorry I know they aren't on your list but most of these are dual purpose and have weight to them. Oops also almost forgot my late great Shelby who was a Barred Rock. She was my buddy.
. This is what I have and they all fly to at least 5 feet off of the ground to get to my roost in the coop. RIR's, Black Sex Link, Phoenix's, Silver Laced Polish(which is on my avatar), and a White Leghorn. Sorry I know they aren't on your list but most of these are dual purpose and have weight to them. Oops also almost forgot my late great Shelby who was a Barred Rock. She was my buddy.
Your question reminds me other oft-repeated joke here on the BYC:
Q: How high can a chicken fly?
A: As high as it wants to.
In any event, the folks here have the best knowledge anywhere. There's a lot of good "flyers", but I have heard again and again that Silkies are notorious 'non-flyers".