Thats a visual man.
I'm not a pro engine builder. In an effort to defend a good design (not perfect, not anemic) the increase from 31-33mm doesn't equate a 60% increase in size, curtain, or flow. Mazda is very smart and I'm sure they know too large a valve will rob your torque.
In engines, there is waaaay more to getting more than adding more.
Too much duration, lift, valve, relief, etc etc etc (again) won't help anymore than too much piston, fuel, air.
There are flow charts for anyone who cares to find them (and please share the links). There is also a long time line in experiences in the aquisition of ability to apply aside from the tools and the numbers alone.
I am not astute enough to serve justice towards this matter in detail. I like the Capri, and believe the motor may be the best engineered feature of the car. There are far more technical forums than this which clarify that opinion very well.