SIGs are typically sighted for a so-called "combat", or "drive the dots" sight picture in which the POI lands directly behind the dot on the front sight. If you like the pistol and want to change that, you will need to go with a shorter front sight, taller rear sight, or both. Here is an article describing the numbering system that SIG uses on their sights, how SIG pistols are sighted, and how much shift you might expect with a change in front or rear sight:
http://www.realgunreviews.com/sig-sauer-sight-heights-sight-numbers/
Keep in mind that because the sight radius on the P365 is so short, the change in POI from a change in front or rear sight height is probably going to be significantly greater than the average suggested in the article, which is more aligned with what to expect for the P226 or 229.
http://www.realgunreviews.com/sig-sauer-sight-heights-sight-numbers/
Keep in mind that because the sight radius on the P365 is so short, the change in POI from a change in front or rear sight height is probably going to be significantly greater than the average suggested in the article, which is more aligned with what to expect for the P226 or 229.