What parts should I double?

[minemax03]

For a school "Band-a-thon" coming up, 11 of us trombones are playing Hymn of Acxiom arranged for 8 trombones. My question is, what parts should we double up on, high or low? https://musescore.com/user/185851/scores/4787840 this is the score. I've edited it, but not to the point that the decision would be too much different. Currently, I put it so parts 4, 5, 6 are doubled, but I'm having second thoughts. Considering doubling 1st or 3rd. Hopefully, you guys have some good input. Sorry if this belongs in the "arranging" category.

[BGuttman]

I think it's where it should be.

If you have players who can handle it, double at least one of the low parts. Also double the melody. Maybe have the doubler play the part down an octave. That leaves you with one more double. Probably doesn't matter too much who it is. Maybe take one of the lower middle parts and put it up an octave.

[paulyg]

One issue with doubling the melody is that solos can phase between the two players. Kind of ruins the effect. I would agree that doubling the lower parts would be a great idea, as the balance in trombone ensembles tends to be very top-heavy.