More cuttings than I expected have rooted for me this year, giving me an excess of certain varieties. Once they are mature enough to plant in the ground, I am thinking about putting 2-4 plants (of the same variety) in the same hole about 1 foot apart. Since I let my figs grow into bushes with several trunks, it seems like this approach would end up giving a larger bush, faster. However, I could also envision each plant growing slower as a result of competition with the others planted so closely, leaving you with no real advantage versus a single planting.

Has anyone done this with their fig starts?

I am still new to all this. But I have read several topics where people braid different varieties together. This way 2-3 varieties can be planted in the same hole. Perhaps, since you have extras, this would be something to consider or experiment with.

Myself, I wouldn't put more than 2 in a hole.  I think they will just end up being too crowded to develop properly.

Many fruit trees are being planted 2,3, 4 in a hole.

You often end up with 4 quarter trees, as branches only grow outward, and not so much in the center.

In trees such as apples and plums, when you are planting multiple varieties in one hole, you have to be careful to plant them in the correct order, with the ones that break dormancy earliest in the north side of the hole, so they don't shade out the others. Not breaking dormancy at the same time is an issue. Differences in vigor is an issue.

If you are planting all of the same variety in one hole, don't see that any of the normal issues would pertain to your situation. If planting multiple varieties, then you would have think it through a little bit. Black Mission and Col de Dame would probably be a bad match because of differences in vigor, for example.

I plant multiples in pots. They grow very well. I fertilize just once in the spring and prune in the fall. I don't see any reason not to plant in the ground this way. Most of the neglected figs in my area suffered die back at some point in the past. They end up a mass of shoots sprawling all over the place. 3 shoots per hole is nothing.

Hi,
I have 2 root-shoots at 1'/30cm distance oriented outwards, planted 5 years ago. They are at 1,80m/6' of height.
While they were young, I didn't have a problem. Now, one made a root-shoot, so they are 3 together.
Finding space for all branches is a bit complicated now.
If you just plan on throwing out the extras, then go ahead and later prune/remove the weaker growers.You could do 3 in an equilateral triangle (each side 1' long )
If you want all to grow to healthy trees with all the sun they'll need, two is the best number. Just plant them oblique pointing to the outside.
If you don't have at the moment space for the extras, just plant them in 0.25Gal ,0.5Gal to 4Gal pots.
Keep them watered and fertilized, and they can stay in pots for 2 or 3 years with no problem.
Lack of nutrients, in ground or in pots, is not a problem, provided that you fertilize a tad bit more.

Now, that I think of it, I have put two cuttings last March in a 2liters/0.5Gal pot, and the both look happy in the pot. But now they are all root-bound.
This case is solved though ... That's a smyrna type strain. So it is of no use in my zone7. Believe me or not, I already removed it 3 times from the compost pile.
Last time I put them back in the pot, the official reason was: Let's see if they  can survive the winter in the outside with no protection - test is still running.