Changing HD’s in a NW 4.2 SFT 3 server

We have a set of Compaq Proliant 1500r servers running NetWare 4.2 with SFT 3. The original HD’s are 3 x 4.3 gig, we would like to replace them with 3 x 9.1 gig HD’s. We have gotten conflicting advice from Compaq and Novell. Any one out there ever attempted this? We are looking for a way to do this without taking the network down completely if possible.