Would there be a advantage or disadvantage in using the silver over the gold or vice versa in a cross to arrive at a Partridge Ameraucana?
If you are trying to get partridge, you would get there quicker using gold (partridge) birds. Personally, I would cross the partidge rocks with wheatons. That way you know what you are starting with. It is hard to tell what colors or patterns are underneath a black or a white bird. Brown Red would probably work, but they are not as common and do not have as good type as the wheatons.
If you have the space, I would cross both was PR males to Wheaton females (pen A) and wheaton males to PR females (pen B).
You don\'t need too many in the first cross. Just a few males and females from each pen.
Next generation cross pen A males to pen B females and vice versa. Hatch a lot from this generation, as many as you have space for. You will hatch a lot of yellow-white chicks and a few brown chicks. Only keep the brown chicks. These are eb and the start of your patridge Ameraucanas.
Grow out as many of the brown chicks as you can. You will need to cull hard, but may not be able to tell which are best until they get older.
You will need to cull for color, yellow legs (recessive so will be carried by those without), light legs versus slate legs, combs, beards, egg color (blue vs green, non blue/green) and Ameraucana shape and size. ( Actually using Plymouth Rocks should help with size).
Subsequent generations, breed best to best and continue to hatch a lot and cull hard.
After your fourth generation, you may want to get a few white leghorns to progeny test your birds. They will help you find many of the lingering recessive genes. You don\'t want to keep any of the leghorn crosses for your breeding flock, but you will want to raise some of the pullets to laying age to test for egg color.
Once you have a nice flock of Partridge Ameraucanas, then you can start lobbying your fellow club members to help you get them into the standard. That is another multi-year project.
Curtis
p.s - You could also start this process using hatchery Easter Eggers for the first cross to Partridge Rocks. I would only use brown hens and black breasted red males. It may take a little longer this way, but not much. Still mostly comes down to hatching a lot and culling a lot. (hope you like to eat chicken)