The HD8+ has 4 30-pin SIMM sockets that can utilize 1Mx8 or 4Mx8 SIMM modules. We at National Amiga have used it with 1x3 and 4x3's, but it has only worked in rare occasions and is not recommended unless you have money to spare.
Using SIMM's with parity is also fine, it will just ignore the extra parity bit (1Mx9 and 4Mx9).
Power Connector Pinout:
Looking at the back of the unit: 1 3 4 5 2 1 Earth Ground 2 Signal Ground (5V ground) 3 +5V RED 4 WHITE (not connected) 5 +12V BROWN
4 PIN POWER CONNECTOR
25-pin External SCSI Connector
50-pin Internal SCSI Connector