Yes, changing the size of the enclosure can have an affect on his desire to eat. What size enclosure is he in right now?
By the way, I am not any good at estimating gallon/volume of enclosures myself, but I did find an awesome gallon calculator on a fish forum:
http://www.cichlid-forum.com/articles/calculator.php
...I kept my hatchling ghost BP male in a 10 gal aquarium for his first 5 months or so - which is huge compared to what most breeders keep hatchlings in, but he had and still has a GREAT feeding response, so I didn't have any qualms about moving him up to a 20 gal that I bought for cheap... but if yours is in something around 20 gal or larger in volume, he could be stressed by all of that open space. I know you said you have a bunch of hiding spots for him, but you never know exactly what he thinks of it all. 
A lot of people in this forum don't like this method, but I use a feeding bin, and I don't feed any of my snakes in their cages. There are many reasons that I do this, so I will try to keep this brief, but here are a few of my reasons:
*once they are feeding, placing them in the bin kicks in their feeding response, as opposed to getting that feeding response when you open the cage to reach inside for cleaning or handling purposes.
*you can use a slightly smaller bin than the cage that your snake is housed in so he could be more "comfy"
*feeding bins are also great to be used for soaking and/or aiding bad sheds
*feeding bins are also great places to put your snake while cleaning his cage - so you don't have to try to do it one-handed
*a feeding bin can be a little easier to completely cover with a blanket or towel, and set in a quiet area to help those fussy feeders concentrate/de-stress
*feeding bins are easy to clean!
I use a tall-sided 19 quart rubbermaid tote with locking tabs on the lid as my small feeding bin. I haven't put any air holes in the container, because I only leave my snake in it for one hour maximum.
There are many more techniques out there - and I had never heard of some of the ones you mentioned, or others that people wrote in response to you here - so don't give up. Also, I don't think that you need to get drastic with any of this. Good luck.
~Rebecca
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1.1 Ball Pythons (1.0 '05 Ghost, 0.1 '03 Normal)
0.1 Dumeril's Boa '04
0.2 American Pit Bull Terriers (40 lb darling lap dogs)