Thanks for the advice, I think I might try and track one down and give that a go.
good luck, 50s aren't really any worse than a 25 in my experience, if you get the pacing right the first 40 minutes of a 50 should be fairly comfortable, the next 40 begin to feel like a struggle and whatever's left feels like a 25.
@Sainsburys_Ed started
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Thanks for the advice, I think I might try and track one down and give that a go.