Well let's assume the average tech is 20 turns. That is 20 months, far too short. At the point in the scenario, only 16 techs remain to Motorized Transportation, I believe. Since this scenario is about par in tech level, with Electricity and Ironclads in the wane of the fifth decade of the 1800s, let's assume the age of Tanks starts around 1910. That is 50 years, or 600 turns. Now we hav overlooked something, the something being that parallel parts of the technology tree could be climed simultaneously, then traded around, bringing the entire world up to pace faster. So let's assume that only 12 techs are needed before trading around for the rest and waiting for tanks to roll in. So 600/12=50, so we need to dilate the tech price by 2.5. Then the avg. tech takes 50 months, and the longest time you can take to research is 100 months. So with the Minimum Turns set to 10 and Maximum Turns set to 100, and the price of every tech multiplied by 2.5, I think things will even out.
About the scenario, before 40 turns, after which Infantry rears its ugly head, this scenario is REALLY fun. I can't quite put my finger on it, but I think thst it's because it's in the middle of nearly every extreme. Some scenarios have ridiculously large amounts of units, often taking 15 minutes or more for the human turn alone. Others leave you with barely any, making early offensives difficult. This scenario has a very nice balance. Also, it somehow manages to remain detailed and deep while keeping the scenario load time under half an hour. You can even jump straight into the scenario, as everything is so simple, yet deep. Detailed, yet not overwhelming. Or maybe it's just me.