Has anyone any experience with handloading the Hornady flextips? I am wondering if I should omit the length of the plastic tip when measuring C.O.L. and just measure to the metalic tip of the bullet.

No, measure the complete length. You should be aware that the factory loadings have cases that are trimmed shorter than 'normal' length. This really is of no large concern as you can just seat the bullet deeper. Having done some reloading work with the new 'gummy tips' I can tell you that it will be impossible to get the same velocity and accuracy from your own loads. Hornady has done an outstanding job on this ammo. Good luck with your handloads!

A Big Thanks for the Hornady paper, I have not seen that until now. Fortunately or unfortunately depending upon your point of view, I am loyal to Alliant/Dupont so RL-7 is my choice, now to trim some case(s), but all these remarks about accuracy have me concerned a little.

I was able to use full length cases but you have to crimp over the edge of the ogive AND the loads has to be lightly compressed (to prevent magazine set back). This is not unlike what Buffalo Bore does with the Speer 350 that also does not have a crimp groove located properly for the 45-70. It's fine if you wish to shorten the cases but it is not mandatory unless you are shooting a load that does not fill the case. For beginners, I'd say just use the Hornady brass made for the bullet.