Hard Jelqs are a kin to Clamping which are exercises not recomended to beginner for they are “high injury risk” I would advise you to milk the 60% erect jelqs first and them move up to either clamping or hard jelqs but it is your meat and you decide the risks you are willing to take. You can burst a blood vessel or several and it my hinder you progress for a long time. However if you are careful you may see some decent gains.