Holy crap that is a big puppy. I thought mine was big but he's just a wee one compared to yours! Hopefully you get his growth/diet issues under control and he matures strong and healthy.
I've read some absolutely crazy results from the DNA tests (which is why I think they are still marketed as basically, "for entertainment purposes only") but I am going to throw in another vote for Leonberger.
I hope its all taken care of for now, although thinking I have to increase portions he is getting too skinny for my liking - despite the weight.
Oh and had some good news last night
The samples are at the lab, so the 2-3 week countdown starts now. I may be wrong but as I understand it the more mixed the breeding and the further from pedigree lines a dog is the more the results go all over the place. The more limited the gene pool of the breeds involved the more accurate it is. Theres also the way genes are inherited with really mixed dogs, two puppies from the same litter could show a different "calculated ancestry" because one has inherited a breed trait from the mothers side and the other from the fathers side instead at that position.
With his size I cant see him being hugely mixed for too many generations. Its got to be a fairly narrow pool of giant dogs. Whats relatively common over here and that sort of size? English Mastiff, Bull mastiff, st bernard, newfoundland, great dane, leonberger, a unlikelly possibility of some recent tibetan mastiff. I cant imagine that sort of size being thrown out with a long line of mixed size mongrels. quite a few of the giant breeds have been through genetic bottlenecks in the not too distant past. That said not long ago I did see a pretty large mastiff\lab\GSD Not too long ago, it was bigger than the few "pure" EM's Ive seen locally. I think perhaps locally we have a small strain of EM's, I bumped into a lady who has an adult EM that she bred from and she said was smaller than falco and that was a couple of months ago...
Leonberger could well be in the mix as far as I know only two of the giant breeds have his webbed toes, the newfoundland, and the leonberger that allegedly got their toes from the newfoundland. I dont see there really being more than 3 or 4 giant breed dogs in the ancestry.
We had him down at the beach the other day and there was an adult brindle english mastiff there, and falco was already taller, though not yet as chunky or round as that dog.
Its all fun and games guessing what might be in there, doesnt really matter at the end of the day, the important bit is hes a fantastic temperament dog and the family love him, but would be interesting to find out what did make up his combination of features.
, I was shocked that after all the time Ive spent looking into the breed I hadnt heard it before Ive spent ages looking into alsorts about them, coat genetics even and didnt know they had webbed toes lol 
