No matter where you put them, please make them consistent from one tee to another. Left side front, right side back, middle of the pad...whatever the location, do it on ALL the tees. That way there is little question about which way the pad faces. There are some courses where a pad is in the middle of a field with other baskets all around, and absolutely no way of knowing which way to throw, because every sign has been in a different place relative to the tee and basket.
I do agree, well off to the side and not quite at the front of the pad is a fairly safe bet. There will always be someone to complain. Maybe not knee height, but maybe 3' up so it's below shoulder height for a 5'6" person, too. Not everyone falls into that category, but the line has to be drawn somewhere.
disc golf, tubas, ol'time jazz, baseball...maybe not necessarily in that order!