FWIW I think much of it comes down to personal abilities; - whether believed or perceived.
As a lone cyclist my measure is what I have done before and the cycling I have undertaken recently. And I wouldn't want to embarass myself, nor uncessarily hold up a group on a ride I wasn't ready for. - Having been on some rides, (not CC ones), where there were riders who were clearly "out of their depth"
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As it happens, I'd have joined
@ColinJ 's June ride, but for helping run a snorkelling club on a Saturday. Sunday would have been better for me, but it seems from posts elsewhere, that Sundays are not a good day for others.
I have provisionally said "Yes" to your July ride as the club is on a summer break on that date, but as much training I do for the lumps and bumps you have planned, SWMBO.may have a final say as my wedding anniversary happens to be around that date.