Yes thats one of the joys of fitting a T Crown, it will be worth it when you get it right.
Take it very slowly, just a mm at a time. If it is too long the gap between the Crown and the case will be too visible and you wont be able to close the Crown Guard lever and if it is too long you could snap the stem. You may need to Trim , Fit it and test it a number of time including fitting the CG, which might take a while. Hope you ordered more than 1
good luck
ST4