SF mastersites

[blubee blubeeme]

These SF mater_sites give me a real tough time trying to figure it out and
try to find github mirrors whenever possible but I need to figure this out.

I'm trying to download: https://sourceforge.net/projects/spacenav/

PORTNAME= freespacenav
PORTVERSION= 0.2.3

MASTER_SITES= SF/spacenav
DISTNAME= libspnav-${PORTVERSION}

I would think the version above would work since it leads to:
https://downloads.sourceforge.net/project/spacenav/libspnav-0.2.3.tar.gz

but that doesn't work!

The documentation on:
https://www.freebsd.org/doc/en/books/porters-handbook/makefile-distfiles.html
5.4.2.2. Magic MASTER_SITES Macros
also leaves me more confused that relieved.

Can anyone help me sort this out?