Suggestions on a 3 in 1 commode for over the toilet for a man?

My parents are using a 3 in 1 commode over the toilet to make the seat higher and to give them arms on either side to make getting up easier and safer. They are both heavy and tall. We are using the Medline Heavy Duty Padded Drop Arm Commode. They like it and it is stable, the problem is for my father to use it. The splash guard (the bottomless bucket that goes over the toilet) is round, not oval shaped like the toilet. For a man who sits down its either too far forward for defecation or too far back for urination. We're finding that even with the bucket pushed forward the pee sometimes sprays on to the floor. Have others had this problem? What is the solution? Is there a sturdy over the toilet commode that you have found works well for men?
Thank you.