I don't think the way of termination is the problem - I think using a narrow terminator with a wide drive is.
Some wide SCSI devices insist on proper termination of the full bus, so if you're just terminating the lower half (narrow), they won't work. Better get a wide terminator, an adapter with half terminator or like moto suggested, switch your cabling to wide.
U2W devices lack a termination option in general, if it's an SCA drive, you can get a terminating adapter.
