Sounds to me like someone cut someone cut some corners not using Fanfold, and or tyvek.
If you want fome under your siding You want to look at your facia, rakes and window trim!!!
When I aluminum trim windows (as most folks) I bend 1" into the wall to receive my J channel that is 7/8". and that will resses my siding to trim 1/8".
You need to post again buddy how far you can build out, with out going past thees three points.