I'm certainly no expert, and others may take issue with my opinons, but here is my experience. Hand shock has never really been an issue for me, as it just doesn't seem relevant , perhaps I am just a bit of a Neanderthal ( a lot of people certainly think so). I shoot mainly Hill bows with straight or dished grips.
I find that a different grip is beneficial. Hold the bow firmly, not necessarily a death grip choke hold, but a strong, solid hold down on the heel of the hand. You don't lightly grasp it, but you do hold that sucker. With tradtional longbow style grips such as straight or dish, a lower heel down grip sort of comes naturally for me. My arm is slightly bent, but that is my natural style that was there even when I shot recurves.
I think some people make too much out of the severity of hand shock, or perhaps they are just more sensitive to it than some. Probably a firm, low heel grip will make all this a manageable thing. Or, to put it another way, if you don't worry about it, it won't become a worry.
Some on the forum have stated that they have had very significant problems with hand shock and will totally disagree with me, but the short answer is "No, you will not break your arm without a perfect longbow grip - whatever that may be!
In short, shoot the longbow and concentrate on the fun and don't worry about hand shock. If it does becomes an issue,some of the form experts can give you far better advice than I can. Enjoy!