Barrel of fun!!

.... when I was skint my Commando lost all its oil and seized the n/s big end. The con rod, which ended up a weird shape, had taken a chunk out of the forward cutout. I couldn't afford to have anything professional done especially after needing a crank regrind and new conrod  etc so I just smoothed the ragged edges with a half round file and continued to do many miles on it.

The "work" is done. You are already running with clearance so finish the cuts to equal depth then radius the corners to form almost a semi circle at the bottom of the relief. Dress the cut edges so they are smooth and your done. Dremel and files will do it. Neatly stuff the bores with cotton rags and tape the joint faces to prevent ingress, then when you finished wash down thoroughly.

they are clearance for con rods, that's all, so dimensions are already big enough, as already said. Also check there are no cracks around the edges which couldn lead to further bits dropping off in future ( unlikely but possible!)

Does the engine have standard con rods or have different rods needing more clearance been fitted hence the modifications.?
As already stated,  just need tidying up with a file.

Best regards,  Al.

There is a good chance that its a 99 barrel that needed some extension to the clearance slots . I would check there is enough clearance at the top for the fatter 650 pushrods ,otherwise no problem. Later barrels may have been a bit sturdier on the 650 with a bit more metal in the casting ? .