This is the same recipe I use. It's a wonderful crowd pleaser and it is great on sandwiches. I like to omit the horseradish and instead add 1/4 cup of crushed walnuts to mix it up every once in a while.
I made this recipe to the letter and the one problem I had with it was the horseradish overpowered everything. My solution was: I added 1 TBS extra of mayonnaise and 1 tsp extra of mustard, then it came out fine. I didn't add any salt, because to me, most hams have enough salt in them already.