I will say this (and probably be drawn & quartered for doing so) .....while many Sieger show people purport that their dogs are not nearly as fat as AKC/CKC show dogs, they are NOT in working weight at shows......not if you want to do well. Or at least not how *I* (and apparently also *you* ) define "working weight."
If you want him to do well, you'll probably need to add 10lbs at least. They don't want to see ribs showing.
I personally think that adding weight for shows is STUPID and I refuse to do it. This is a WORKING breed and if they can't be shown at working weight (and do well), well, I'm not gonna worry about it. I know for a fact that going between the AKC show ring and a
TRULY working weight dog (can
see ribs, not "feel them"

) is about 20lbs (according to my friend who shows/finishes her own dogs in breed, then trials in Agility, to Top 10 level placements).
To play with the weight of a dog like this is not healthy.....no more than it is for you to continually add/shed weight. More weight is harder on the body, and over the long term life of the dog, less healthy.
If the work is what you love, keep him at working weight and take the rating you get at the show. A rating does NOT change what your dog is, how your relationship is with him, etc.
Most of what I've seen in show rings (AKC and Sieger) would NOT last very long on a SchH field working bark/hold at their show weights.
If I need to increase weight (I often do with Banja during the more active months.....she sheds weight like she sheds coat!), I simply increase food, and perhaps add some fattier meats. When taking weight off a dog, I decrease food and increase exercise.......the simple basics you've known all your life.
