The extensions will be standardized at 4", and the frames are standard at 28" with extension option frames able to adjust from 24-28".
I will add a note though....the way the pack rides on your body is extremely adjustable. The hip belt has two grommets which allow you to raise or lower the belt. So, I can make that 24" frame ride like a 22" frame or even a 26" frame with just a couple changes in suspension.
If I was day hunting in brush I would want the frame low at shoulder level and I can do that. I can also raise it up for packing more weight.
A side note- last week I hauled a 20 something pound climbing treestand plus a 50 lb sandbag on the frame for a mile with the frame in its short configuration. That ~75 lb awkward load is the upper limit of what I want to haul without the extensions. It did fine but would have been more comfortable with extensions in.
I think my turning point will be in the 50-60 lb range. Below that I'd prefer the shorter frame, above that and I will prefer the extensions.
