I havent heard of Shelby's recommendation but I definitely plan on looking into that. At 25 mcg a day I would not think the effects would be noticeable. I have my own curiosity as to how fast on average t-3 level comes back. If there is a supply of t-4, as I would think there will be, when you use an artificial form of t-3, than I think once the body realizes that t-3 is circulating it will come back fairly rapidly. Until then I would think the the storage of t-4 will convert to t-3 in the body.
T-4 is stored for later use by the body. If there is an artificial amount being consumed from a synthetic form of t-3 that meets the body's demands, than it has no reason to use the storage. Once the body senses a lack of t-3 circulation, than it will begin the process of producing once more. This could be after the storage of t4 is used up or during. Thyroid hormone is much more important than testosterone which is why I think the body keeps the thyroid levels in check very strictly (except for cases of hypothyroidism naturally caused or consumption or radioactive iodine).