Probably a heretical approach, but how about ignoring the provided thick and hard material and skinning the sucker with 1/16 basswood instead? I ended up with two Sakonnet Daysailer kits somehow. The first I fought like a dog to use the thick stuff they provided for "planking" and it's OK but far from fun. Having a second kit on hand I tried using 1/16 basswood instead. Still needed a wee bit of water and some heat and gentle persuasion but the hull looks better, the job went quicker, and all seems perfectly fine. Just need to remember you don't have all that wood on the hard chine so care in refining the line with sandpaper is needed.
I haven't done the Lobster Smack yet, it's waiting in queue while I finish up a Mighty Mite tug and the two daysailers. Odds are I'll do a Dumas kit or two before I get back into the Midwest kit world. I sure do recognize that hard unyielding planking material you are fighting with through.
Cheers, and maybe running and ducking!
Stan