I just installed the KTM guards today. Yes, the front and back 'clamps' of the guards, where they go around the the handlebar, seem at first too small. But with the bolts entering from the front, and a little elbow grease, you can the get the nut on the first couple threads. Then just go back and forth tightening the upper and lower. The plastic of the 'clamp' is soft and you will eventually get them snugged.
Boy, they sure clear my V-Stream windshield with room to spare, unlike the stockers! I'll be interested to see if wind management or vibration is different. But I have my bars filled with copper-jacketed BB's, so the vibes haven't been bothersome at all.