How to avoid the funky look of -JT and -SE-?

Q&A
1

I was surprised by the funky look of the Transverse Mercator projection (-JT) when combined with some -SE- on the plot borders (tuned for extra visual appeal):

tissot11
tissot11487×647 148 KB

Those Tissot’s Indicatrix are not supposed to look that spiky. Is this some clipping at the borders going rogue?

gmt begin tissotJT pdf
  gmt coast -R0/360/-80/80 -JT-15/15/15c -Bpg30 -Bsg90 -Ba30 -B+t" Transverse Mercator projection (-Jt -JT)" -Wthinnest,gray -Glightgray
  gmt plot indicatrix.txt -SE- -Gred@50 -Wred
gmt end show

indicatrix.txt (826 Bytes)