Ever thought of A Seabird Seeker, at Patrol Speed (65kts) can do 6hrs endurance or normal speeds about 4.5 hours endurance.
Go the party bus (PN68). Spare engine, 9.5 hrs endurance and much better ventilation in the newest models, gets there faster, loiters longer, cameras can be deployed and retracted (IR, coronal discharge, hyperspectral etc...), high wing and the observer is available if the bubbled observation windows aren't enough.
DA42? Little company called Airborne Technologies in Austria is run by Diamond's former Manger. Sure his opinion is qualified. They have a (severance) DA42 Guardian that has big label on the nose saying "Airborne Technologies prefers Technam."
(They are developing a specialised 2006 surveillance platform.)