Stiff VS Regular

I am currently looking to purchase a new driver and am on the fence about getting a stiff or regular flex. I am playing with the X-18 Irons, uniflex shaft. I do not know my swing speed, but stand 6 foot 4 (if that matters). I have been told to error on the side of caution and get the regular, and it is difficult to find a fitting pro right now in snowy northwestern PA. My driver now is the ERC, 10 degrees, and it often fades right and goes low. Any help?

Size doesn't matter here - I know a guy 5'9" that swings at 130 MPH. At 6'1" myself, I can get up to 118, but usually clock in at 108.

Your swing speed and how far you carry your current driver are helpful details and would certainly aid in making a suggestion. What is the current make, model and flex of your driver shaft?

My Callaway ERC driver has an Aldila 65 Stiff shaft, and the 3 and 5, also ERC, have a firm. I can carry my driver 250-275, but often fade right. I am not sure about my swing speed...but I believe it is around 100.

Unequivacobly stiff. Learn to shut the face down through impact, or check your swing path.

I have the same left to right issue, but it's a path thing for me. When I come from the inside (versus over the top) I get a nice long ball with some draw action.