Another thing I noticed is that the eTrainer looks very light in weight, and since it has no seat, your weight would not be available to help keep it in place.

This may not be an issue if it is only used in passive mode. However, if it is used in an active mode (assuming this is even possible), you may need to bolt it (and the chair you sit on) either to the floor, or to, say, a large, flat piece of wood placed on the floor.