Hey Bobby

Sounds like you have it all under control so well done! Good that he wasn't stirred up. But just for future it is probably best just to introduce things and see the response. Do you know of Geoffrey Maitland - the Manipulative physio who died recently. He was really picky about only introducing one thing at a time and assessing the effect each technique has. that way you can really assess the relative benefit or harm of each technique.

I was def planning on utilizing the overload principle. No its not a true 15RM, I just thought 3 x 15 with 2kg weights was a good place to start with the flexor/exentsor strengthening as the patient was able to complete 15 repetitions with relative ease. Then I was gradually going to progress to 2.5kg, 3kg, 4kg etc.. Do you think that is okay?
It is probably is a safe way to proceed as you are just gradually increasing the load. However it isn't really following an exercise science approach. Ask yourself this: why are you doing the exs:

1. to strengthen the flexors and extensors
2. to improve the endurance of these muscles
3. exercise the muscles but avoiding overstressing the joint.

If it is point 1. then you are probably not being very effective. No overload no gain. And for a young male You need to be working him within the range of 8-12 reps near to fatigue. If you are going for 2. then that is probably what you are more likely to achieve - however even then you still need to be working near to overload. If 3. then you are being conservative and safe. If you are trying to strengthen but want to reduce the sharing forces across the joint One other factor to consider is the length of the lever arm. The closer the weight or resistance is to the joint (ie shorter the resistance arm) the less sharing forces across the joint. So heavier weight but more proximal eg wrist weight rather than holding a dumbell