It doesn't look possible but can you capture partial amounts using the Craft admin panel? E.g. Authorize $1000, then capture $700.
Also, when performing Captures in the Stripe panel, these transactions do not show in Craft in the Order Transactions box. This looks like a bug to me.
Last, if we can't perform partial captures in Craft and need to do it in Stripe, how can we mark Orders as paid?