Suggestion........
Measure the weight of the tounge resting on a flat surface.
If it is less than 750 lbs then you have room to work.
If it is very low , such as 150lbs for example, then loosen the bolts on the vertical tounge rest and slide it forward in short increments and pull the boat forward. Ideally the sterns transom should be parallel to the bunk boards at their ends. I see you have about a foot until you reach this???
I understand this is NOT the designed trailer for your boat but yo can balance it out quite good for easy towing and safe operation. Ideal tounge weight depending on the class of your hitch and your tow vehicle, is a couple hundred pounds.
If you have a light truck and a heavy tounge weight you will effect the steering geometry of the front end. I pull with a Ford F-350 Dually with a class 5 Titan hitch, so I can load the heck out of it!