I had a hard time on RPM blast last night. Twice I broke the knot when almost finishing the job (used two strings as the result). I was using the Parnell knot there. Somehow I find the string not as flex so the single hitch was hard to close the loop ... Should a starting clamp be helpful in addressing the problem? On the other hand, when I strung Gosen Polylon 16, it is even more stiff, I was able to complete without this kind of mishap. Maybe Gosen is tougher than RPM, ? Any opinion on what kind of knot I should use on stiff string like RPM blast and Gosen Polylon 16? Thanks.