Are these lines better:
0 Name: 1-4con15.dat
0 Author: Michael Heidemann [mikeheide]
0 !LDRAW_ORG Unofficial_Primitive
0 !LICENSE Redistributable under CCAL version 2.0 : see CAreadme.txt
0 BFC CERTIFY CCW
4 16 15 1 0 13.8585 1 5.7405 14.7824 0 6.1232 16 0 0
4 16 13.8585 1 5.7405 10.6065 1 10.6065 11.3136 0 11.3136 14.7824 0 6.1232
4 16 10.6065 1 10.6065 5.7405 1 13.8585 6.1232 0 14.7824 11.3136 0 11.3136
4 16 5.7405 1 13.8585 0 1 15 0 0 16 6.1232 0 14.7824
0 // conditional lines
5 24 15 1 0 16 0 0 15 1 -6.213 13.8585 1 5.7405
5 24 13.8585 1 5.7405 14.7824 0 6.1232 15 1 0 10.6065 1 10.6065
5 24 10.6065 1 10.6065 11.3136 0 11.3136 13.8585 1 5.7405 5.7405 1 13.8585
5 24 5.7405 1 13.8585 6.1232 0 14.7824 10.6065 1 10.6065 0 1 15
5 24 0 1 15 0 0 16 5.7405 1 13.8585 -6.213 1 15
0 // Build by Primitive Generator 2
I had indeed forgot to use the rounding for the third and fourth vertice on optional lines. Sorry!
0 Name: 1-4con15.dat
0 Author: Michael Heidemann [mikeheide]
0 !LDRAW_ORG Unofficial_Primitive
0 !LICENSE Redistributable under CCAL version 2.0 : see CAreadme.txt
0 BFC CERTIFY CCW
4 16 15 1 0 13.8585 1 5.7405 14.7824 0 6.1232 16 0 0
4 16 13.8585 1 5.7405 10.6065 1 10.6065 11.3136 0 11.3136 14.7824 0 6.1232
4 16 10.6065 1 10.6065 5.7405 1 13.8585 6.1232 0 14.7824 11.3136 0 11.3136
4 16 5.7405 1 13.8585 0 1 15 0 0 16 6.1232 0 14.7824
0 // conditional lines
5 24 15 1 0 16 0 0 15 1 -6.213 13.8585 1 5.7405
5 24 13.8585 1 5.7405 14.7824 0 6.1232 15 1 0 10.6065 1 10.6065
5 24 10.6065 1 10.6065 11.3136 0 11.3136 13.8585 1 5.7405 5.7405 1 13.8585
5 24 5.7405 1 13.8585 6.1232 0 14.7824 10.6065 1 10.6065 0 1 15
5 24 0 1 15 0 0 16 5.7405 1 13.8585 -6.213 1 15
0 // Build by Primitive Generator 2
I had indeed forgot to use the rounding for the third and fourth vertice on optional lines. Sorry!