On my BX 2660 the brushguard did not use allen bolts , but it still used hex bolts , that when removed caused tricky holding of guard before it drops to floor or to hold it in place to reinstall while holding head behind frame.
So I bought some longer bolts ran them thru the frame holes so heads where backwards, then before putting on brush guard put a locking washer and nut on to hold the bolts in place permanently, so now I have four bolts sticking out that I can easily hang the brushguard on so that it doesn't require holding, while I put the nuts in place that actually hold brushguard in place. (I went with nylon lock nuts cause they look pretty too)
yes this causes brushguard to be moved forward the thickness of those of locking nuts to make bolts permanent , but no clearance issues occurred. And now it is one hand work with ratchet to get nuts off, no need to hold other end of bolt from turning. Added bonus is side panels slide on and off easier too.
I think they ended up being three inch bolts I bought (and reversed) instead of the stock 2 inch ones