  Nanostructured solid boron-hydrogen compounds have been suggested as target
and fuel for laser fusion, offering improved laser-plasma coupling, avoiding
cryogenic fuel handling and fuel pre-compression and ultimately allowing a
transit from DT- to aneutronic pB- fusion power production. We describe the
scaling of the different energy loss channels ({\alpha}-particle escape,
bremsstrahlung, hydrodynamic expansion work, electron heat conduction) with
mixed fuel composition using partial inverse gains (Q's) which allow a simple
superposition of losses. This highlights in particular the negative synergy
between these loss-channels for such mixed fuels: the dominance of
bremsstrahlung over fusion power at low temperatures forces a shift of
operation to higher ones, where the plasma gets more transparent to
{\alpha}-particles, and hydrodynamic and heat conduction losses increase
strongly. The use of mixed fuels therefore does not eliminate the need for
strong precompression of the fuel: in fact, it renders achieving burning plasma
conditions much more difficult, if not impossible. A recent suggestion to use
tamping of the fuel by cladding with a heavy metal would only reduce
hydrodynamic expansion losses significantly if the cladding could cover most of
the fuel surface, in competition with access to laser radiation. But even if
tamping were perfect, this would not reduce the remaining three loss channels -
in fact it would have a negative effect on burn propagation, as the escaping
energy would not heat surrounding fuel, but only the cladding material.
