You can't go wrong with more height, so the top of the ladder may be the best choice unless you plan to use something different. If you should use the ladder, I would recommend grounding it well, if it is not grounded. My ladder was not grounded at all and I recently added a ground strap to the quick disconnect mount and grounded it to the frame. I have seen an amazing difference using my 75 meter hamstick. I've not tried it on other bands yet but will very soon. Good luck with it.
Jim ~ W4EWA