slow cooking a 30 lbs inside round

I cooked a lot  of these over the years. I used Top rounds on my buffets and for all my roast beef needs on the front line. As long as it's carved thin it's tender. The problem I had with a real large Top round was it took so darn long to cook. They were a PITA to have ready when need. The good thing was they hold well in the warmer. I know I cooked mine at 350 degrees in a convection oven. All that being said and because the roast will hold in a warmer cooking ahead is fine. In most all cases the top round comes with a fat cap that protects the meat from direct heat. I would also roast it on a rack so it doesn't over cook from the bottom up. Because you starting out with a big cold chunk of beef it's hard to put a time on it. I would put it in at a lower temp and adjust the temp along the way so as to assure the roast is done when needed.