[Dominik]

I see what you mean. However, that applies only to a very radical cam profile.
Any reputable cam manufacturer should be able to assist you here.

Remember, duration is advertised from the point when the lifter moves 0.050" inch up.
The same cam with a 1.7 ratio would cause the lifter to raise earlier, resulting in more duration.

A roller cam's profile features a much bigger area under the curve, because the valves open more quicker. A roller cam with 260 deg advertised duration would fill the cylinders much faster at low lift than a flat tappet.

It would also sound more radical as a flat tappet, "sounding" like more duration.

Generally, I would not use a higher ratio because it results in more force on the valve shafts and stems. I consider it more a "saturday afternoon" hot-tip than anything else. Especially since you build a complete new engine, including camshaft.

Camshaft ramp rates have improved dramatically in the last years due to better material that I wouldn't hesitate to specify the ramp I need - in discussion with the cam manufacturer.

Dom