Richard,
Thank you for the warm welcome. Interesting site, I assume it is yours (Aquamist). Love the theory and application of WI/AI and was looking for more info online while also looking for yet another alky injection system for my latest project (a SC Z06 Corvette). Looking at your system, I have decided to isn't for me for a couple of reasons, but your forum is very much of interest to me because the world and wealth of knowledge on this topic is relatively small.
As you mentioned, some people are shooting very high volumes of methanol. The more you shoot, the more fuel you have to pull out from the main fuel system. It's no secret that you can make more power on methanol than on gas. The more alky that is injected the more you're converting the engine towards a methanol fuel source (more boost and timing can be added). Most people are not adding anywhere near the volumes you mentioned. I find myself using about 80% pump gas and 20% alky by volume under boost... but keep in mind that you need to add about three times as much methanol as you would gas to maintain the proper A/F ratio. Although I'm injecting 20% alky, it only accounts for about 7% of my fuel source. In other words, if I'm injecting 20% of my overall fuel in the form of methanol, I'd need to reduce the gas required from 100% back to around 93% to keep the proper A/F ratio. So while at first glance it looks like you'd be running "pig rich", you actually are not.
You can use the basic method of tuning you described (ramping up the alcohol flow until the engine bogs down and then ease it back a little) and it will work to get a safe tune with alky or water, but it's far from optimal. I use EGT, KR, and A/F ratio together to nail down the tuning... works great.
If I were you, I would strongly consider make a kit that is compatible with straight methanol so your customers have the option to play with alky. IMO alky offers many of the same attributes as water, but also adds some bonuses (like additional fuel, drastically lower IAT's, increased octane...) You can add WI to a FI engine and it will control detonation quite well, but when you shoot straight methanol you not only control detonation, but you also add power with no other changes.
Designing a system for use with alky is very simple... just make sure everything is corrosion proof and rugged. I don't think your pump will do the job for a high volume alky system. From my experience you need a pump that will handle high volumes, is pressure adjustable, and can't have metal parts in contact with the alky. In the US we have found this pump to be cheap, very rugged, capable of very high volumes, and will do 60 - 180+ psi...
http://www.northerntool.com/webapp/w...&issearch=2687
Add in some SS braided lines, good fittings, and an excellent boost referenced controller and you have magic!
Scot