TL;DR
The shocks are pretty easy to change, but you have to take the entire suspension off the board. They use lotsa locktight so use plenty of heat on each bolt. They also have an excellent youtube channel with a buncha How-Tos.
I just changed the shocks on the rear suspension a few days ago.
I kept the springs, but replaced the entire rest of the shock.
FYI, the shocks don’t alter the turning radius at all. Mine turns pretty good, but you have to really lean into it and trust the board…
You can buy different bushing from Propel on their site.
The board comes with the mid strength Grey ones… you can get stiffer Black ones of softer White ones. The bushing are the sorta A shape and slide in behind the Top plates, the ones that have PROPEL and ENDEAVOR on them.
The Virtual Garage has a video on it.
Im only 150lbs so the stock springs and bushings are pretty perfect for me.
You’re correct about the springs being setup to keep the suspension close to the top of its travel. Since you’re a bigger guy, you might want to actually replace them with stronger springs.
Also, if its a used board, the shocks may need replacing anyway.
I just got mine on Amazon, they’re just Mountain bike shocks.
https://www.amazon.com/dp/B0C3VH2P62?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1&th=1
You need the 125mm version, but you can choose whatever spring weight you want. Im not sure what the stock white ones are… 400lbs I think…
Enjoy your new Endeavor…