Interesting, several contributors have read much about towing. One, painters are only used to tow in protected waters. Two, a stout towline, in this case 1/3 to 5/8 inch would suffice, and the length should be longer than a wavelength to prevent the towed boat from surfing into the towing boats transom in a following sea. Open ocean wavelengths are too long to make this practical so a small drogue to keep the towed boat from surging is necessary. And finally, towing a small boat over 5 knots in any situation is begging for trouble in the form of capsizing, bow nosing under a wave, damage to towed or towing boat hardware and chafing of the towline. Towing a boat that is a third the size of the towing sailboat is not recommended die to compromised maneuverability keep the towed vessel size at 25% or less, hence dingies tend to be 8’ to 10’ so your typical 30’ to 45’ sailboat can tow and maintain good steering. With ribs you see a lot of ill-considered tows about, but just because one can do so doesn’t mean it’s good seamanship.