If the other bows dont have cases maybe try this.
Cut it and layer the foam and some corregated carboard between the bows as you see fit.
And find a carboard box to stack them all into or just put a piece of packing tape all the way around to keep them secure to each other so they don't bump around and use a cardboard divider to keep other stuff in the trunk from knocking into the bows.
I used this technique for hunting season when stacking my equipment behind the seat of my standard cab toyota pickup. The 2" thick foam kept every secure and never had an issue bumping the sight out of aligment. The carboard kept my gear seperated from my bow. I think I found the matress topper at walmart or big lots and it was around $25 or $30.