You don't really need more than 6 unless you need one of the 7 INT feat or High-technicality build tbh. Crafting is super lenient rn due to hypercerebrix and house bonus. Max per is nice to eliminate lighting penalty and increased the range which you could score 95%, so sniper is well worth it to have 18 Per, unless OP playstyle revolves around "mobile close combat" sniping with lots of disable, caltrops, and "escape" feat (sprint, Strafe). In this case, 13 Per is good enough.
Since you pick Ambush, lighting ain't a problem anyway, and first turn molotov is pretty strong opener
Also, sniper with trap is pretty damn strong, in a metagaming perspective. You could block other potential enemies using bear trap and mines, by the time you shoot the "main" group, everyone in the map will be alerted, caught in bear trap, and soon will die from multiple mine explosion.
Although idk if sniper actually louder than grenade, since mk1 can only affect ~40 tiles, which basically adjacent room