I’am a friend of overforking…
My 29er hardtail frame was designed for 100 mm fork – and use it with 130mm fork. Fantastic!
Recent project: my Bossnut V2 had a 130 mm Sektor fork. Put a 150 mm Fox fork in. Felt very strange and out of balance. All the weight was on the rear and rear shock was bottoming out.
But simple fix: the original Bossnut has a 45 mm stem and 2 spacers under the stem. Changed it to 60 mm stem and no spacers and moved the saddle 15 mm to the front as well. All is perfect!
But the weight balance of full suspension bikes is very sensitive.
In your case, hardtail: not as critical, but 40 mm “more travel” means you will have to modify the geo to get the balance right again.
Bit longer stem?
Overloading the frame: love overforking but I try not to overload the frame. No crazy jumps with such an bike! I check for cracks quite often as well…