I've owned two 650C highracers, a Volae Team and a Bacchetta Aero, and the things have no problem keeping up with uprights, assuming one has developed their "bent muscles."
Highracers are a nice transition from uprights to bents as they tend be more familiar to upright riders as far as height and components. They also mix better with uprights on rides.
To the OP, I assure you that a strong rider on the flats has no problem keeping up, quite the opposite.
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Keep the chain tight!