Both assumptions are at the outer edges of the normal envelope for road race frames. To make it enjoyable to ride, you should probably aim for >50mm.
Theres plenty of people riding on bikes with a 75 deg headtube and a standard road bike fork with 43 mm rake. I even do that myself. To a comparison that gives a trail of about 45mm. Seems fine to me. Quite lively yes but no where near unrideble. Do you really think less than 50mm is that bad?
Theres plenty of people riding on bikes with a 75 deg headtube and a standard road bike fork with 43 mm rake. I even do that myself. To a comparison that gives a trail of about 45mm. Seems fine to me. Quite lively yes but no where near unrideble. Do you really think less than 50mm is that bad?