Dan, you fell victim to two things:

The glens conservative rules and the issues with a long track,
and

The regions desire to ensure the event made money.

Historic run groups are a regions way of making the entry count higher, and it protects them from losses.

But when things go haywire, and you're at the glen, and the region has sold lots of entries, there is little room for schedule adjustment. So somebody loses.

The Glen also, (Hard to believe with all of 3 cows within a mile of the place) has noise curfews, so there is a definate end to the available time. And add the fact that the Glen would rather rent to:

The Porsche club
or the BMW club,
or any driver ed club,
....or host a NASCAR event,

and it becomes apparent why it can be a real crapshoot for us SCCA types as to whether we actually get full races in when we're there, more than at any other track.