split your 8ft loft into 5ft x 6ft and 3ft x 6ft 5ft will easily house 12 cocks the 3ft will also easily house 12 hens on perches so would be ideal to race either widdowhood or roundabout thats if its an 8 ft x 6 ft loft your 18ft loft 6ft seems quite large for 4 pr of stock more like 8 or 9 pr that would leave you 2x 6ft sections for y/bs or you could take 2ft off the stock and 2 ft off one of the y/b sections giving you 4ft x 6ft for a feed store/basket store