1. The anime is not a Canon, it's similar to fanfics in its nature, because every season was created by a different team of directors, each with their own quirks and interpretations. Each one pulled in a different direction, practically ripping the storyline apart.
2. The Season 4 (SuperS) had deviated so far from the rails that in the Season 5 (Stars) the director was replaced with another guy who tried desperately to bring everything back on track. So most of what happens in the beginning of that season, namely in the episodes 167..172 (girls moving to the High school, etc.), should be put *before* the Season 4 (ep. 128) if you wish to keep your sanity.
3. Ergo, if you want to use the anime as a Canon, you should repair it first! Otherwise it isn't fitting for that role.
[a cry from the heart]
And for the Goodness' sake, do not exploit the plot holes! Just patch them as you see it fitting for your story, or just ignore them! Ask someone who knows! Use material from the manga, at last!
Because all these shamanistic dances around the plot hole called "Great Freeze" drive me mad!
[/a cry from the heart]