An approximate time scale for single-chain folding, τ s , was determined as the average time for two monomers in the chain to come into contact (defined as a center-of-mass separation of 7 Å, averaged over 80-100 (or 20 for flexible chains) independent single-chain simulations), consistent with the definition used in previous work for the folding of semiflexible polymers. We will refer to this as the "first-contact time". This definition of the folding time assumes that, once in contact, the chain does not unfold, which is consistent with the observed behaviour. It also assumes that all chains fold (form at least one contact) within the simulation duration; however, while all the longer chains, and flexible chains of any length, folded, only ≈75 % of the 10mers with the regular-flexibility backbone folded within the simulation duration. For those that did not fold, the first-contact time was set to the simulation duration (e.g. 25 µs for 10mers) for the purposes of calculating the folding time. The calculated folding time in this case is therefore a lower bound on the actual folding time.