When to harvest cucumbers for seeds

[DeanRIowa]

I want to save seeds from Poona Kheera cucumber plants I have been growing.

Some seed saving sites says to allow the cucumbers to overripen for up to 5 weeks.

Can I pick a normal ripe cucumbers and allow the to ripen off of the vine, because if I overripen them on the vine won't that cause my plant to produce less?

thanks,
Dean