It seems like it should work although we could probably debate the idea about a 7mm hole flowing enough air, but if it works for you great.
Be careful on the type of solenoids that you use, you must keep in mind that the air temperature there will be >300 °F and some solenoids may not last that long at that temperature.
On another note the Microprocessor controlled version of the Turbo Guard (Blow Off Valve) should be ready in a week. This addition is pretty cool, as it allows you to adjust almost every possible setting on the blow off valve (i. e. open time, re-apply cancel, clutch cancel, throttle lift, and time of lift).
The biggest draw back of the original design and Steve's design is that the unit will only work when the throttle is completely released to an idle position (or another preset position). With microprocessor we can activate the BOV from any position you want; say from full throttle to half throttle. The unit works by measuring the amount of APPS voltage dropped in a set period of time.