I agree, sibling to sibling is the best bet for double recessive projects. At least that's how I've decided to go for my double recessive projects based on the research I've done. I plan to go visual to visual, holdback one male and put him to all his sibling sisters. Of course the more females you get from that first visual x visual clutch, the better your odds will be of hitting the double recessive with one of the next generation pairings.

Your project sounds really good, it sounds like you have some really nice animals to make the project super exciting and hopefully if the odds gods are with you, super rewarding as well

I look forward to seeing how your projects progress, I wish you the best of luck!