Bioequivalence and Bioavailability Forum

Dear all & especially D. Labes!
I played around with package PowerTOST and found a counterintuitive result.
I tried to get an 'optimal' total sample size (pilot + main study).
Assumptions: CV 25%-35%, T/R 0.95, 80% power -->
require(PowerTOST)
expsampleN.TOST(alpha = 0.05,
  targetpower = 0.80,
  theta1 = 0.80,
  theta2 = 1.25,
  diff = 0.95,
  CV = 0.25,     # variable: 0.25-0.35
  dfCV = 12-2,   # variable: 12-24
  alpha2 = 0.05,
  design = "2x2")

I varied the sample size of the pilot study in the range 12-24 and calculated the size of the main study. I got:         CV = 25%    CV = 30%    CV = 35%
pilot  main total  main total  main total
 12     34   46     48   60     64   76
 14     34   48     46   60     62   76
 16     32   48     46   62     60   76
 18     32   50     44   62     58   76
 20     32   52     44   64     58   78
 22     32   54     44   66     58   80
 24     30   54     42   66     56   80
This puzzles me in two respects. Though the size of the main study decreases, if the size of the pilot increases (estimated CV more reliable), the estimated total size also increases. Fixed sample size for CV=25%-35% are 28/40/52. Another point is the difference between small and large pilots dependent on the CV. In my example for CV=25% the ratio of the total sample size (pilot 24/12) is 1.17, for CV=30% 1.10, and for CV=35% 1.05. From these results one could suspect that for higher CVs, the size of the pilot study becomes more and more irrelevant?!

Sancta Juliem, adsta!

Now I did it the 'old fashioned way' aka based on the _X²-distribution (Julious, Chow/Liu, Patterson/Jones, Gould), alpha 0.25 and got:
        CV = 25%    CV = 30%    CV = 35%
pilot  main total  main total  main total
 12     42   54     58   70     76   88
 14     40   54     56   70     72   86
 16     38   54     54   70     70   86
 18     38   56     52   70     70   86
 20     36   56     52   72     68   88
 22     36   58     50   72     66   88
 24     36   60     50   74     66   90
Higher numbers, but a similar pattern. The ratio of the total sample size (pilot 24/12) for CV=25 is 1.11, for CV=30% 1.06, and for CV=35% 1.02.
Shall I abandon my pet hypothesis and suggest "the smaller, the better" in the future?