If I had a slider, I would put Super Track mod on it in a heart beat. It is much more impressive in person than in the pictures.
As for your antenna location, I have my comm antenna mounted on the belly. The aft two bolts go through the spar flange and the front two are bolted to a stiffener with plate nuts. Only once have I ever had a problem talking to the tower while on the ground and I found out later that even Skyhawks had the same problem at that location.
My GPS antennas are all stuck on top of the glair shield. I covered my glair shield with a sheet of loop Velcro, which works out great! It looks and feels like felt and has held up very well for the past 10 years.
My transponder antenna is up against the firewall, on the right side, just inboard of the fuel vent. The ADS-B antenna is on the left side, just inboard of the left fuel vent.
Everything works as they should with no problems caused by placement close to the main gear leg, which was my biggest fear.
This setup helps keep the wire runs short, avoids trying to figure out how to get all those wires through the limited holes in the spar, reduces weight, and makes future maintenance easier.