Also if you are going to run tensionerless you can do it without a half link. Removing half an inh from the chain (using a half link does this) is like adding or removing 2 teeth from the from or rear sproket or 1 tooth from each.
Using a BMX chain would make any alignment issues worse as it less flexible laterally. I run both of my SS with 8 speed chains with no issue. I do tensionerless as well.
Wrap your chain arround both spokets and bring up to join and measurewhat faction of an inch you need to remove or take away to join. Add/removing 1 tooth takes or adds 1/4″ to chain length.
Either this or get a push up tensioner.