I have been sailing peters channel step boards for about 10 years now. And I like them. I'm certain you could sail one before you buy. The channel forces air under the board for early planing, the flats on either side reduce the wetted surface area when planing and the step increases control at high speed by reducing tail walk. Peter is also aware of the problems associated with nose size on these types of boards. he would be more than happy to explain the theory to you. you can also see them being made at different stages. I think he is building 4 or 5 of different widths now.
you shouldn't have any trouble in chop on a formula, or swell either. but when the chop starts to form closer together and get steeper almost turning into small waves things can get scary. For light wind hooning I reckon go 85cm or wider. you will probably end up only using that setup. lately more and more people are getting formula boards at caloundra and bigger sails. At first they feel a little awkward because they really like to sail upwind but after 3-4 sessions you'll overcome that. You can carve them to your hearts content. I sail at Wello, Caloundra, Lake Catharabah, Victoria point and Mooloolabah. all different conditions. the only place I have noticeable board control issues is just at the markers at Wello at the end of the channel. the swells stack up. but once you pass it into the deep water with the ocean swell it's not a problem anymore. wide boards are great in ocean swell, the ride down the back of the swell is awesome.
you could use your 7.5 to start with, depending on vintage but a bigger sail would be a must. I would definitely recommend a deviator too.
the guy you see at caloundra is either me or peter

, I use my north IQ and Peter uses his retro. If you ever want a closer look at a board and you see me just come and say hi. if you want I could introduce you. lately the 95cm boards and 9.5+ sails have been cooking me I lighter winds so I'm going wider and bigger.
I have known peter a long time. he taught me how to sail and then taught me to be an instructor, I sail with him regularly, and he is always letting me to try his new toys.
Justin.