It would be a gamble, not worth taking, from my point of view, especially as you can get most of the needed items at your destination, with a bit of planning.
Strictly speaking, you would need to make a "Dangerous Goods" declaration when shipping or flying with metol. It is a low risk item, but a dangerous one. Formally, it is classified as a Toxic Solid, UN No 2811, Dangerous Goods Class 6.1 (Poison), Hazchem Code 2X (not violent), Pack Group III (low danger). Phenidone would be very similar, speaking from experience of importing a small quantity into Ireland. All that means, is that a white form with red stripes needs to be filled by you, and accepted by the carrier, for it to be shipped. That includes couriers, like Fedex, UPS, or the post office. If you comply, and pay the extra fees, which can be exorbitant unless you often ship dangerous goods and have negotiated those fees, then it is perfectly legitimate to ship it, subject to local laws and customs rules.
Not declaring it as such, however, puts you at a serious risk. From an airline perspective, they want to know what they carry, so they can be sure they are not cargo-load-full of Metol at a time, that they have space for bunnies (I presume that would be a low risk item), and that they only take a reasonable amount of total risk, with regards to all of the goods they have accepted on board at that time. They would not want to carry a half-of-the-cargo-load of sodium sulfite next to to a half-load of hydrochloric acid, but they may be able to carry each, on its own, or in a smaller quantity. Besides, they have no obligation to carry anything they do not wish to carry, and so they need you to declare it. Ultimately, the captain will make the final decision—even if formally accepted by security, captain can always say no to the carriage of anything (or anyone). Strange laws we have created for ourselves, but there is a shred of sense in them.