Richard would be the best person to ask.
I also forgot to mention Ron Perrott's new line of dive modules (sorry Ron). These are superb with twin piston ballast tanks (similar to Engel tanks but with a few differences). I'd recommend one of those for your boat- should slip straight in, and you'll have a very nice boat indeed.
If you want to get some ideas, and see various boats in action, you should come along to a Dive-in (link to website is in signature). We get boats with most types of systems at these events, so you will be able to see for yourself what you think is the best route to follow.
No system is perfect- they all have pros and cons, the trick is deciding what features you are happy to with or without.
Andy