What are pitfalls of "hard mounting " tranny vs rubber mounts?

At this point I am looking at suspending from the four side mounts, the engineer geek in me says mathematically they will be more than sufficient. The racer in me says I am screwed if I do not go rubber mount. On plus side I am very handy at welding cast aluminum so I am going to mount it hard watch it close and regroup if she breaks. I am building car for wife and she typically doesn't thrash them like I do although she is not above donning a helmet and dropping the hammer at the track! Did I mention she drinks beer and loves to camp in a tent and hunt deer and elk for days on end? And she fishes better than I can? Oh yeah love me a redneck girl! And she patches me and the boys up after hockey games when we try to do things only young hockey players should do. All of which is why I am building the Demon for her as a daily driver.
And I forgot the two down legs will result in forehead gashs, I have removed them now as my bracketry evolves. I am starting to box it in now, I will try and get some pix today. The two down legs were remenant from OEM mounting plate. I really liked them but the ground clearance was becoming an issue. Thus the side mounts.