Here's how to add in the volume control to the v0.24 board to make it into v0.3 guts for the Niftymitter Home and Gig.
Step 1: Solder in the pot
Using a craft knife, carefully cut the trace between R1 and R2 (the 10k resistors at the line socket) and C1 (the electrolytic capacitor).
This image shows the underside of the PCB.
Solder the wire from leg 1 of the pot to the board at the pad where R1 and R2 join. Solder the wire from leg 2 to the negative of C1. Solder the wire from leg 3 to the ground.
Step 2: Glue the pot into the board
Hot glue the pot onto the top of the spacer first. Place the pot in the hole of the middle hole of the housing, apply some glue to the bottom of the spacer and offer up the board to it, taking care to make sure the board fits within the appropriate area of the housing. The spacer should sit in between C3 and R1 - it is best to check this before glueing. With the blobs of hot melt included, the pot's base should be 13mm off the circuit board.