I am like Wheever, between a 52 and 54 frame. To determine the size I fit myself to the top tube of the bike, much like is recommended by Sheldon Brown (Revisionist Theory of Bicycle Sizing). I brought a plumb line (string with washers) with me so I could roughly set the fore-aft at the correct position (roughly KOPS) and when on the hoods determined which size had my face over the fork tube/stem. Then I determined which frame felt too large. It turns out the 54 was too large due to handlebar reach as it would require a short stem (under 80mm) to not overreach to the handlebars. Keep in mind I have a short torso and long legs for my size.