<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px"><div id="yui_3_16_0_ym19_1_1461346333504_2586">Hi Sean,</div><div id="yui_3_16_0_ym19_1_1461346333504_2586">I have been studying the head maximum pressure chart on Psubs and found that the pressure rating increases the same amount proportionately with thickness.</div><div id="yui_3_16_0_ym19_1_1461346333504_2586">Is there a limit to this? </div><div id="yui_3_16_0_ym19_1_1461346333504_2586">Thank you</div><div id="yui_3_16_0_ym19_1_1461346333504_2586">Hank</div></div></body></html>