It’s been a while since I’ve posted on this forum and I know this is an old topic, but I figured I’d respond for future reference.
I have both my solar and UV sensors extended but differently. Like the OP I opted not to cut the UV sensor’s cable due to the price of the sensor. I learned not to long ago from a Davis employee that the UV sensor can be a bit temperamental when attached to long extension cables even the Davis cables.
I have my solar sensor spliced into a 100’ Davis cable and installed on the roof. The UV sensor is connected to a cheapo 25’ phone extension cord purchased at Fry’s electronics. Both sensors seem to work just fine. I used the offset settings in Weather Display to fix the accuracy issue plus normal drift in both sensors.
One thing I will say though, on the solar sensor make sure the connections are absolutely watertight for the obvious reasons.
Initially I used those yellow cap wire splices that you snap in with pliers that Davis includes with their extension cables, but due to the fact those are permanent and the solar sensor has limited amount of cable to work with I started stripping and twisting the wires together and dipping them in clear unscented candle wax and placed the connection in a green Christmas light plug protector. I haven’t had any issues since.
Just my 2 cents.