I agree, had I had access to silver based Marans, for my silver project or copper blues for my blues, I would have used them,..Honestly I would have used the chance to introduce silver based Marans. I intend to catch up on that, or I use english silver duckwing Welsumer.
however, if you use silver Welsummers, I'd recommend you talk to Hen-Gen from the coop, as they have mentioned the tenacity of 'autosomal red' in the shoulders of their silver Welsummer males