Hamish, the rocker on a 9’ HPLB is much different then a 9’ semi - typical 9’ HPLB 4.5N, 3.5T, typical 9’ semi 6" N and 3" tail. Two different beasts that ride completely different. Sounds what you’re calling a semi is more in the fun gun category, essentially a wider gun with a more relaxed rocker.
If you like heavier boards, hard to go wrong with a 6 bottom/6,6 top. Want even more weight, go 6,6/6,6.
Discuss your needs with the shaper you select, he’ll know what rocker to install, how to glass it based on your feedback…trust him, he’ll have done this before…
Thanks for all your comments Guys, very much appreciated the 9' HPLB looks like the board I will ask my shaper to template from, could you explain what difference in performance the rocker difference would make please Icc.
4.5N verses 6N and 3.5T verses 3.0T , I don't have creditable knowledge in understanding rocker dimensions and would appreciate any information before I approach my shaper.
HPLB rocker is going to feel more like your standard longboard, as the sweet spot will be closer to the tail due to the extra rocker curve there. The rocker sweet spot on a semi/fun gun rocker is going to be further up as there is a bit less curve in the tail. And that is an over simplification statement.
And the rocker has to tie in to the bottom plan - single to double concaves? Flat to V? And assuming a 2+1, where do you want your side fins? Some shapers will set them at 16" or further up, others at 14" or so.
Since you’re a longboarder, you will be more comfortable with a longboard rocker. And as your max range is 8’, you really don’t need a semi-gun rocker. If you want a little extra forgiveness, can always get a little ‘tip flip’ installed while keeping the overall lower front entry.
Talk to your shaper, ask your questions, he’ll probably whip out a blank, explain exactly what he is going to do, and you’ll learn more a lot more in that meeting then any of us could ever impart on this forum.