Smaller heads on the hardware makes it easier to tighten down and have them just below grip, along with needing to make sure they are tight enough down that the nylock holds the nut on and not come loose, which often happens when shorter deck bolts are not done up enough. Some brands of deck bolts like Shortys come with low nuts in the 7/8" packs, which is why I like them as they fit perfectly on regular baseplates done up just right, with the smaller heads nicely into the grip. Other brands have the regular nuts, which on regular baseplates with 7/8" bolts, often cannot be done up tight enough without pulling them into the wood a long way. This is where 1" deck bolts are usually a safer option.
As for the pressure on the board, there are more breaks from the upward cut of the baseplate into the truck than anything to do with the hardware, so when you land too hard on the nose or tail, the board flexes and the truck edge puts pressure on the deck.
If you round off the edge of the baseplate, mainly at the inside edge in front of the kingpin (but I know some people who do both ends), then it will not cause so much of a sharp pressure and give you a little more before the board will break.
Also using something like a thin rubber riser / bike tube / other similar thing with 1" bolts will prevent so much pressure from metal to wood as well, but I know a lot of people who will not do that and break a lot more boards because of it.
There are a few options anyway.
The other thing to note is for people who break a lot of boards, anything with carbon fibre, or other material will usually help the board last a lot longer and there are lots out there from a number of brands, which work out to be of reasonable value when you consider the extra cost beside how long the boards last. These include but are not limited to Powell Flight decks, NHS VX decks (Creature, Santa Cruz), Crail Pop Secret (Girl, Chocolate) and there are a few options from Dwindle (Almost, Enjoi, etc) as well as other brands in specific areas / countries that use those same technologies, eg in Australia we have Elan Redline decks which hold up really well and Folklore Fibrelite too.