After a lot of trial and error this appears to work for me. Just before I set off for a ride I push the Whoop up my arm a fair bit. At least 3 fingers. Feels a bit strange but I do get some pretty good HR readings that are fairly close to my Garmin chest strap. If anyone is struggling with consistent HR might be worth a try.
Only concern is I might start to get a strange tan line 
I have found the bicep band is the best for bike rides. I think it has something to do with the way I hold my hands on the bike handles, it just doesn’t allow for good contact of the sensors with my skin. The bicep band doesn’t seem to have this problem.
Of course, your experience may be different.
I have a bicep band but not tried it yet. I can imagine it is better but I am not sure I want to keep switching between Wrist and Biceps when I ride, bound to forget more often than not. I need wrist for ECG & BP which is the main reason I purchased the MG. I am aware that Wrist based is not the best but the wild results I get when on the wrist is bizarre. I can live with a few anomaly’s but I have hit highs that I couldn’t if I was 20. If you read through the community lots of people are unsure of the Whoop 5/MG’s performance when it comes to Heart related things 
Thanks for the suggestion though.
