What would happen...

[lifeoffaith]

...if I split a 4 x 4 x 3 deep coop and 6 x 4 run into two to house a silkie pair on half and a buff Orpington roo and 3 hens on the other. The split would be wire, either chicken wire or possibly a tighter wire if needed.

 

[ChickensAreSweet]

Your run size will only be 12 square feet for each group. That is a little small IMO unless they are able to get out to free range or to a larger pen outside of that one.

General quoted rule of thumb on BYC is 4 square feet per chicken inside coop PLUS 10 square feet per chicken in run. The more space the better in general.

 

[donrae]

I think it would be looking for behavioral issues. The original, full size you're giving isn't even large enough for 4 buff Orpingtons. Overcrowded birds can do very, very nasty things to each other, even traditionally docile breeds like silkies and Orps.