Are their any problems with the poles or flags being fragile?
Not that I can tell. The mast is cut from Lego, which is a harder plastic than modellers usually use. The bowsprit is a possible risk, but it seems firm enough - the flag comes from a Dreadfleet ship so it's fairly rigid.
Where does the big wheels come from ?
They're from a 15mm artillery piece - can't remember which, but that was the best source of biggish wheels that I could find. I covered the hub with a little shell pattern shaved from the same Dreadfleet ship mentioned above.
