Need your help here.... I have been experimenting with several string setups in my UT (18x20) and in order to determine tension for mains and crosses I have consulted tension adviser (http://www.stringway-nl.com/en/TAonline/calc.php). It recommends slightly higher tension in the crosses e.g 21.6/22.5kg (48/50lbs). I have used this recommendation with several all poly setups and the shape of the head remains unchanged after stringing. I recently started testing hybrid setups (gut/poly). For my initial test (vs team/alu soft) I strung at the tensions mentioned above but did not like the way it played (too much power, lost control) so decided to go up with the tension in the gut mains and slightly up for the poly crosses (24/23kg-53/51lbs). I noticed though that after stringing the shape of the head changed a little (3mm shorter top to bottom , 2mm wider left to right). I planned on testing even bigger differential between mains and crosses like 2.5kg (5lbs) or even 5kg (10lbs) but now i am hesitant to do it since I expect the head shape change will be even greater... Is there an "acceptable" range in head shape change? Should I try it? What's your opinion on this? What If I want to try that bigger differential in tension should I go to a different frame or 16x19 string pattern? I appreciate your help on this.