I have in our network implemented SFH, we had 60 frquencies to use. i put aside 30 frequency for hopping (10 *3). the gurd bands between other operators and hopping and BCCH frequency were taken from the remaining 30(BCCH frequencies + GB). for me i had to reserve 10 frequencies per sector because we have high configuration sites which give us up to six TRX’s per sector. as you said gurdbands are very importnt otherwise you will have interference between you BCCH and Hopping channels. do not forget to adjust you quality power control and handover threshold after implementing SFH….