why the foam heads ? or were you trying to create bass poppers
Most of those are very heavily dressed with marabou and wont sink quickly but will have decent movement, remember "less is more".
If you can get those flies deep enough then they should work. Try squeezing out all the air before casting them out the first, basically pre-soaking the marabou otherwise it will float on the surface until your sink tip sucks it under
example - the bottom fly I posted has only 2-3 turns of marabou and used from the tip end using only the long thin fibres. It also has, if I remember correctly around 20 strands of white ostrich. The 2-3 turns of white marabou was put in only to help fill out the profile to achieve the effect I was going for.