You have a good start by understanding the stack and reach of your frames. If you know the reach of your handlebars and the angle of your stem and the amount of spacers then you can duplicate your position by using this online frame comparison tool www.velogicfit.com go to the products drop down menu and select frame comparison and scroll down to the bottom of the page for the free access. Input all the specs from your old bike (select in the drop down menu) and adjust the stem and spacer info to get to the new position you want on the new bike. You will need to know the specs of both frames. This will get you an Hx Hy measurement which is the center of the bore for the handlebars. If using the same bars then no problem, however if they are different then add or subtract the difference of handlebar reach measurements to your current setup ( add if new bars reach is greater than old, opposite if shorter). That will give you the position to the hoods! Makes the numbers equal as possible and your positions will be the same, if you want higher or lower, more reach or less, make adjustments within the calculator.