Today I managed to get into a tricky tile on Bodmin Moor to increase my max square from 19 to 22.
On the same trip I also completed some gaps in my cluster:
it now runs all the way from Land's End to Bristol - is there a challenge for the longest cluster?
Not on Veloviewer itself. On a Dutch forum we have an internal challenge about this. To be at the top your longest distance within your cluster should already be over 400k. Nothing compared to one German tilehunter who has a cluster extending from the Adriatic to the Baltic Sea.
The longest straight line distance entirely inside your cluster is a bit of a different metric, I suspect.
It wouldn't be inconceivable to extend my cluster down to Land's End, there's one ride there already as a catalyst. But it wouldn't be a straight line to Oxford.