Will the Magpul MOE SL line of hand guards fit the triangular shaped hand guard cap? I ordered Magpul's new mid-length SL hand guard and tried to fit it on a factory Bravo Company Mfg mid-length upper last night. Try as I might, I couldn't get the bottom front lip of the hand guard to go into the cap. The top section installed with no problem. I compared the new MOE SL hand guard to the older MOE hand guard I took off and the older one has a groove for the bottom edge of the triangular cap to fit in. The new MOE SL hand guard doesn't have the groove. Has anyone else had this problem?