To provide some idea of the magnitude of what the waffling is about -

A thick layer of insulation over an antenna wire is just
uniformly-distributed capacitance loading. As with ALL transmission lines,
an increase in capacitance per unit length results in a reduction in the
propagation velocity and a reduction in the resonant length.


Capacitance increase depends on wire diameter, diameter over insulation, and
permittivity of the insulating material. The velocity factor due to
insulation thickness in the case of a long, straight, antenna wire, can be
estimated as follows.


d = wire diameter.
D = diameter over insulation.
h = height above ground.
K = permittivity of insulation.

K can vary from 2.5 to 6 depending on material.


Calculate A = K*Ln( 4*h/d )
Calculate B = K*Ln( 4*h/D )
Calculate C = Ln( D/d )

Then VF = Sqrt( A / ( B + C ))

Decrease in antenna length due to insulation = ( 1 - VF )*100 percent.

And unless the insulation thickness is like 1" diameter coax with the braid
stripped off, for ordinary HF wire antennas at ordinary heights the pruning
will be lost in all the other things which might need a teeny bit of
pruning. As Roger advises "cut long and trim to fit". In practice, if a
tuner is in circuit, after taking the obligatory end-effect into account,
then I would guess pruning is seldom needed on simple wire antennas.
----
Reg, G4FGQ