RE: Lowering of engine on thrust line
As old git says, a flying tail is usually assumed to be a fixed surface rotating about some axis. The illustration does not show where this axis is and that is very important. In general flying tails present several difficult design problems, primarily getting enough strength in the hinge points to prevent unwanted displacement or bending under air loads plus making sure that the fore/aft placement does not cause serious problems in airodynamic balance.