I don't care for most commercial rawhides for two reasons, one: many of them are made in China, and two: they're often chemically treated.
THe hard part about mastiff puppies is finding puppy chews in sizes large enough for them. Apollo has always enjoyed sticks, but they may not be something ou want him chewing on in the house. From my work I can get the heavy duty cardboard tubes used to hold rolls of photopaper. They weigh almost 3lbs, and the cardboard is over an inch thick. It takes my two weeks to demolish one, but they both enjoy them. Results in bits and peices of cardboard paper everywhere, but thats what vacuums are for. I have a video somewhere of Arty working on one, I'll see if I can find it.