I just received a response from a forum on The High Road in regards to my problem, quoted below. Turns out, just need to figure out how to muscle it open this first time, then maybe look at a mod.
"As an owner of several original LeMats I have been lucky enough to compare them with the ones produced by Pietta.
On the reproduction they did not use a small end mill to cut the slot that the lever fits into the frame. Because the slot has a radius cut they had to make the spring shorter, which because the leverage is now on the near side of the pins' pivot point it wants to flip to the open position.
Several people have commented on that in posts.
To compensate for that Pietta makes the lever extra tight in order to keep it in the closed/locked position.
The lever will with stand the force necessary to open it.
On my reproduction shooters I have removed the lever, re-milled the end of the slot in the receiver and made a longer spring that puts tension past the pivot point so that the lever spring closes the lever properly.
Also I replace the retaining pin with one that protrudes a little on each side of the frame as per all of the originals I have seen.
The Colonel"