speaking of 3.5" floppies, is 720K R.I.P.?

I don't have an answer for the other gentleman's query on 720RPM floppies but I recently discovered that new 3.5" drives appear to no longer support 720K media. I purchased a number of Samsung drives for a project where I am converting a system with 5.25" drives to use 3.5" and I found that these drives have left out the media density sense switch all together! They no longer have any way to detect the lower density, 250kbps media and run at 500Kbps no matter what is installed. I needed the 300 rpm, 250Kbps capability to be compatible with the old 5.25" stuff. What's particularly nasty is that I chose these drives, Samsung SFD-321B, because I had a recent datasheet that clearly showed they supported this mode-- until of course they arrived and the switch/sensor is not even installed! Is this true of all 3.5" drives now? This might explain why 720K 3.5" drives are selling for $285 on eBay :-( I'd sure like to find a way to force the drive into 250Kbps mode-- I can't believe the chips don't still support it-- I just need a way to figure out where the sensor is supposed to connect and hard wire it to 720K mode. Any ideas on how to do that? Chris