Just prepare a Laemmli type separating gel, insert acomb and leave off the collection gel on top.
Large proteins can gel stuck at the border to the separating gel.
Also, only use true gradient gels. The size of 600 k is not uncommon at all. Please if any constructive advice I will be apperciate. If you have already tried that, I think that I have heard that low-percentage agarose gels might work better for a protein that size. I have never run anything over 200kD, so have never needed to deal with this problem.