Hi Steve ,
The ability to load the rod n cast heavy poppers depends very much on the strength of one's upper body , in my case when using SP78H SHP , I can cast comfortably 100 ~ 125 gr. lures but that does not mean heavier lures can't be cast optimumly using SP78H SHP . Many friends of mine use 150 ~ 180 gr. chugger using the same rod but they are in general much younger than me ( gonna be 60 at the end of this year ) and some are bigger built than me ( I am an overweight n unconditioned 5'8" bloke ) .
The SP series blanks are built from a higher modulus than the WV series blank , I would not compare SP78H SHP with WV80XH because they are of different line ratings , I would say SP78EX-H is stiffer than WV80XH , for the same line rating and for the stiffest rod from Carpenter range , SP78UHL SHP is the rod .
As for max. drag , SP78H SHP is rated for max. drag of 12 kg for line rating PE 6~10 , compare this with WV80XH which is rated for max. drag of 15 kg for line rating PE 8~12 and with SP78EX-H which is rated for max. drah of 13 kg for line rating PE 8~12 .
Please do not compare these ratings with other brands' rating because these ratings are very subjective in nature , these ratings are meant to be compared with other Carpenter rods only . Comparing them with other brands may lead you to nowhere because the ratings are subjective in natures .
Jon .