The reason your are liking the foam is most likely becasue it is easier for you to cut so it gives a better end profile.

If you really need to have that bottom section of the hook engulfed in yarn then you have two options:

1. Add a section of yarn to the bottom
2. Use more yarn on top.

As the density of the yarn increases, the tighter the egg becomes and the more it will "poof." Teh drawback is that it will also become more bouyant and behave less like the real thing.

I tie them very sparse--on purpose, and the steelhead I angle to and guide to do not care.

I think the yarn has a better appearance when wet and holds it's shape better. Strong thread, minimal wraps (jam knot, 3 tight wraps to secure, lift up the yarn and 3 tight wraps to finish, then whip and snip), and very sharp hair-stylist scissors are the keys.