While I respect and recommend staying within your comfort zone… you can do a test piece on the bench to raise your confidence level.
A solid solder joint in a tough spot can be simplified by pretinning the parts, this just means clean and flux, then heat and apply/melt solder onto each part (the outside of tubings/inside of coupling) and completely wipe/flick excess solder leaving just the silver color on the parts. Reflux and assemble, The fine solder layer left on each the parts ensures proper flow/bond when heat is applied to the assembled parts….with just heat and a touch of solder you will complete the joint.
Chuck
