To relieve the control friction without re-engineering, buy youself a can of silicon spray lube and spray with the direction tube supplied between the nyrod inner/outer. It won't relieve inbuilt friction due to a poor setup, but will reduce the higher friction you'll experience with SIG nyrods. Whilst I like SIG designs and their kits, their included hardware is 'ordinary' and that's being kind. Their nyrods are plain dreadful when compared to Sullivan or DuBro product. More friction, plus they react (stretch & shrink) more with extremes of temperature fluctuation.

If spraying with silicon lube doesn't reduce your rudder control rod friction to an acceptable servo load, you'll have to discover what is actually causing the friction and fix it by re-engineering the problem out. NB: Fix the problem on the ground before flying. You can't can fix it once in the air.

Listen to Uncle Ted and Crashem about the rest Papa, especially about the importance of range checking. If I may expand in more detail upon their sage advice.

Antenna
On taildraggers, an external antenna run needs to be along the top of the fuselage to avoid a risk of snagging ground FOB.

You can run it inside the fuselage if you want, but it's better to have it externally mounted for regular inspection and minimisation of risk of interferance. It's smart to engineer an easment (circular servo mount grommet or fuel tube will do) in the hole where the antenna exits from the fuselage. On the Four Star this is commonly through the cockpit roof itself or just aft of the cockpit, although there's not much solid there to mount it on and you need to either run a conduit up the back of the cockpit rear former or make up a small plywood mount for it between the stringers.

You should have a internal strain relief (button is ideal) on the antenna. The average RX antenna length is overlong for the Four Star 40 fuselage. Extend it to the top of the fin (mounting) and then just let the excess 4 inches or so trail. If you must run it through the fuselage, DuBro sell protective antenna shroud for that exact purpose.

Tailwheel
Wheel collar (preferable), or solder in place with a washer.

Axles
Wheels rotate around the axles. NOTE: The 'axles' (threaded bolts) SIG supply with that kit are sh*t. Do yourself a favour and buy a pair of DuBro or Great Planes axles. Again, fasten with wheel collars. Don't ruin a good set of wheel hubs by drilling them out because SIG were too tight to include decent axles in the kit. (That REALLY suxs SIG!) When the Four Star meets with its end as it inevitably will, you will find the aluminium undercarriage, wheels and axles will be useful for another model. I think just about everyone must keep a Four Star perpetually in their plane inventory, so when you prang it, you will almost assuredly end up building another. Happy landings!