I just got a pair of the Malvern chukka boot. In the 5 last I wear an 11.5D. Based on reviews I ordered this boot in an 11.5E. The width feels fine in the forefoot--my feet are snug but still have room to move.
My question is about the fit in the heel. They feel a bit loose unless I lace them extremely tight and really push back against the back of the boot. They fit securely then. Does this sound like a) matter of the width being wider than normal b) a bad fit and therefore makes these a no-go c) something than can be remedied with an insert of some kind? They are sold out in 11.5D. I'm not used to wearing a chukka like this and so I'm not sure whether this is a significant issue or not.
The Malvern is a weird one when it comes to fit the footbed is lined with memory foam. Because of this it fits much tighter than standard 1 last boots. The Bayfield is another one it has a poron insole which doesn't take up as much space as the memory foam but it still is tighter fitting than others on the 1 last. You can try going up in length a half size or in width a size. If you go up in length it still may not fit and you have to be careful of creasing too far forward. If you go up in width a half size as you found out you often get heel slip. How much you can live with is a personal decision, personally I do not want any. The Alden Barrie last has too much heel slip for me too but I have a narrow heel which doesn't help. I gave up on the Malvern no matter which way I went it was a no go. I have not found a stick on insert to take up heel volume for a boot that works long term. On shoes you can have a piece of leather stitched into the heel but not so for boots. Some people do not mind heel slip but I have no tolerance for blisters due to improper fit. I have 5 pair of shell chukkas by AE (Dundee on 1 last) and also the AE Katmai (4 last) and they all fit my foot great and see a lot of time on my feet. I would not give up on a chukka if you like the look.