R E C U M B E N T B O O M N O T E S
As with many other recumbent bicycles, the boom of the R-20 sometimes has a slippage problem. The boom is in two parts, an inside tube with the bottom bracket and crankset at one end that slides into an outside tube which is the rest of the bike. It seems that pedalling puts clockwise torque on the boom (assuming your chain is on the right side), tending to twist it.
Various solutions to this have been suggested. The long wheelbase R-40 has a bolt and groove arrangement to prevent this.
I was having particular problems with this, since the metal had stretched and the two brazed-on bosses for the bolt were touching before the outside tube fully tightened on the inside tube. My solution of the moment (suggested by someone on the HPV list) is to use a piece of plastic soda bottle as a shim. This apparently also has a greater co-efficient of friction than the metal to metal contact has. It seems to work well so far, though I'd like to give it a few hundred more kilometers before I comment further.