No scientific data to back up or bolster my opinion.
That doesn't matter. You do not hold back to write something in public. That's the only way to get a good discussion and a better idea of what's just a myth or what to watch out for.

Good point, people always try to find excuses. Im trying to rule them out.

Do we mean the same thread about b vitamines and running hot; a discussion between gotap and waccamaw? I still wonder why b12 would run a dog hot. And in what way it differs from Iron when it comes to running hot.

I understand your point. But let's take for example. I have one supplement containing HBM,MSM, a little ammount of creatine , thiamine b1 and maltodextrin. HBM and also the creatine is something that will help train more effective/longer(goes against acidification) and recover better after the training, but also protect the muscle mass. Thiamine helps with converting carbohydrates/glucose into energy. Maltodextrin consist of glucose.
I see nothing wrong with the HBM and MSM, that little bit of creatine will not cause any water retention, the thiamine i don't mind for what ever carbohydrates my dogs will have in its body during a show. Though i remember glucose is a fast sugar and not something you want a bulldog to run on in a show. Now i don't know in what quantities each ingredient is, i do know its main ingredient is HBM.
Considering it's something advised to used at least 20 days prior to an event, also on the resting and taking in mind that this is a greyhound supplement. Would you or would you not keep giving it? I wonder why they advise to keeping it continuously until the event.
The dog will benefit from most ingredients during the show day, but if there's one thing that could work against the dog, like the glucose (although again i dont know in what %) it's better to stop it. Now that im wrote this i think you're better of buying each supplement individually, though you would really have to be careful with the dosages.

Im far from a professor myself, i just try to google for stuff i don't know. Lot of good but also bad information on the net.

So aside from the question what supplements do you cut out in the last week; what do you still want to use on the showday itself.