Bruce, the answer here isn't a larger fellowship, as a larger fellowship won't address the issue of not recruiting for goods that your fellowship isn't producing.
On World #4 our fellowship had an over-abundance of steel and a shortage of planks. Fortunately I had near neighbors who had planks to trade and we were able to recruit more active & equal level people who did have planks to address that shortage.
For me, a 40 member fellowship means a lot more overhead on tracking which players are actively trading,visiting and progressing since inactive players do not benefit the fellowship even if I feel guilty about giving them the boot.
I tend to recruit in several ways: 1) trading partners who are trading a good we're lacking in, 2) actively searching for people near our upper levels who have boosted goods we need, 3) reviewing applicants and prioritizing those who have the boosted goods and level we are looking for.
I haven't utilized the forums to recruit as I haven't seen it done a lot and I am not certain how many players are active on the forums.
You can tell another player's boosted goods by looking at the triangle points around there city: N, SE, & SW.