if you're reading NBR you might have seen my thread about if the cf-27 caddy fits the cf-28. so short answer no, long answer yes.
the're is already a mod by jtstealthuser that requires cutting the magnesium chassi in the computer however i think i've come up with a new way.
by buying a cf 27 caddy for roughly $20-25 and a 44 pin male female cable($9.99+shippng) you can mod it to fit.
if you look at the two from the top the cf28 had its hard drive mounted vertically and the cf27 horizontally. ergo it wont fit completely and therefore compromising the waterproof chassi.
however by using this cable: http://www.cablesonline.net/644fetomaide.html
you can turn the hdd 90 degrees and mount it correctly. i have both the caddy and the cable on the way from the states so i'l post a detailed instruction later if it works, however there is no reason why it shouldn't.