Same here. I purchased the Woodlore boot trees for my walnut shell Daltons but ended up using those for other boots and use the epic in my Dalton's. And most of my boots and shoes for that matter. I have the same issue narrow heels and no arch, on my left foot it has flattened totally over the years. I have custom orthotics both for boots and half length thinner ones for dress which cost $400 for each set. Couple of years ago was in an AE store and they sell black superfeet inserts for $20 and I picked up a pair to try. Turns out they work as good or better than my custom ones. They are half length and work in dress shoes and boots without changing the volume in the toe area but help with filling the area in the heel and mid foot. I only wear my custom ones in heavy hiking or hunting boots now. Even then I sometimes wear the black superfeet instead and walk 8-12 miles a day during bird season without any problem. Most foot docs would give me a hard time for saying so but it is worth a try and your only out $20 if it doesn't work. I would keep the 11.5D and try them in those as they are fixed in width for most D width shoes. They do push against the sides of the shoes or boots but it isn't very noticeable and trees bring everything back in when resting. By adjusting lacing tension I can prevent heel slip but it takes tongue pads in a few of my shoes. Good luck.