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For the PFM these perforated ones, Jan. It is the hub used for the early "21" variants. IIRC these were in use also with the MF although a couple of MF had the hubs of later, solid style.
Actually you should have painted these wheel hubs and tyres separately. And then assembled them together with already painted legs. Unless these are the one-piece casted parts.
You are right, there isn't much there to secure it. Funny that ABT does the same thing as well, to the whole kit!
Want one in 48th and a SterlingWorking on a Halifax to go along side the Lancaster