The stocks and foot stirrup do appear to be the same which doesn’t suprise me at all. The trigger in the nextgen does appear to be Jandao. The Maximus has a trigger that was built in Indiana.. The rep behind Maximus was Paul Vicunus (spelling is wrong I’m sure) the man behind Camx crossbows.
I owned a Maximus, then when I couldn’t find parts I came a crossed Nexgen. I called them maybe Sept of 2016. And spoke to a man there. He told me some of the parts interchanged but the trigger I needed was not one of them. Oddly enough I then ended up with a couple of Native Crossbows which used parts From the Maximus, Parker,Scorpyd and PARTS MADE IN HOUSE IN INDIANA. Parts made by the same people who did machine work for Maximus.
Sadly the gentleman who owned Native and the machinists behind Maximus has passed away. And the machines sold off by his widow. I own 3 Natives and love all 3. One of which holds two Indoor National titles and every state record the IFAA has for the class.
If it helps the last time I saw a Maximus or Nextgen listed for sale it was on crossbowcanada.com . And the site appears active. I would leave off the string stops, adding them could create a week point in a bow that parts may be hard to find.
Good luck in your search