To change lattice pitch (in cm):

! Lattice pitch - 28.575 cm
EVALUATE Tmod   Pmod    ppmB hpitch       mhpitch     
           hpitchm01 mhpitchm01 := 
           346.0  99.91   0.0  28.575 2. /  -28.575 2. /  
           28.575 2. / 0.1 -   -28.575 2. / 0.1 +  ;
[give lattice-pitch value 4 times]
Evaluate ar00: last radius should be 1/2 of lp