@Stonechat I did two rides last weekend, 55 and 30 miles. The legs are feeling it a bit still, but I reckon I'll be fine tomorrow. Chances are the only riding I'll get in between now and the event is this weekend. As the only 100 I've done before was very flat, this one might be one step too far. 50-55 I'm comfortable with. But I've only been further twice... Hence the plan to do a longer, if flatter run this coming weekend. Of course I might benefit more from doing a couple of shorter runs, one Sat and one Sun.
The plan is to register for the 100 on Friday night, so I can start early Saturday, and allow myself nine hours to complete including stops. That way I can take it steady.