To the OP, nice rig! Couple of thoughts: to get your mat's plugs to work as intended, try lubing the plugs and then pushing through the holes, and if still needed use a plier to pull them the rest of the way until they are fully engaged.
Hoe thumb. I've had 3 on my KB-2485. First was a manual, which I hardly ever used. I then bought up to a MIE clamp on dipper stick thumb, which had hydraulics, but was not integral to the bucket pin.
Now I have the final version, also from MIE, and it shares the bucket pin as it's pivot point. It is by far the best yet, and is welded to the underside of the dipper stick in addition to the shared pivot point mentioned above.
One word of caution, I found out the hard way from having no prior use/practice with thumbs, that one must move the thumb to the bucket rather than curling the bucket into the thumb. Otherwise, as I learned the hard and expensive way, the bucket curl can overcome the thumb's ability to resist the enormous pressure of the bucket hydraulics, resulting in a bent thumb cylinder.
This is less likely with the hydraulic thumb that attaches to the bucket pin, but still warrants mindfulness in operation of the thumb. I keep mine fully retracted when not actively using it to grab something. Also do not give in to the temptation to use the thumb for anything like digging, use only the bucket for those tasks.
Personally, I think the full hydraulic package is well worth the money in the long run, if one plans on using a thumb for many tasks, but I understand that it is a personal choice and a budgetary decision as well.
Enjoy your new machine.:thumbsup: