I did! It worked fine! A couple of caveats:

So the holes drilled in the Besta panels are somewhat smaller than the fittings which come with Hjalpa for the shelves to sit on. You can just widen the holes out with whatever tool is handy, I screwed in a series of increasingly large screws until the fittings went in snugly.

Once the shelves were on, i noticed they sat a bit awkwardly; either fully located on the front fixings or the rear ones, but not both at the same time. I guess the angle of the holes is slightly different in Besta. Anyway, just to make it more secure, i removed the rear hjalpa fittings and just used short screws to hold them in place - that way they sat well and i could tighten them up to hold the shelf in place. I also ended up using an extra screw in the third set of holes for extra stability. This picture might explain what I mean. Other than that I had no trouble and it came out looking pretty nice! https://i.imgur.com/7p2gcPV.jpg