Hell, I've got 6 halyard exit holes in my mast, grouped together. Just one of which is probably as big as this wire mess. I wouldn't have second thoughts of doing the hole(s) especially where it's located and supported by the deck.
When an axial load is applied to a piece of material with a uniform cross-section, the normal stress will be uniformly distributed over the cross-section. However, if a hole is drilled in the material, the stress distribution will no longer be uniform. Since the material that has been removed from the hole is no longer available to carry any load, the load must be redistributed over the remaining material. It is not redistributed evenly over the entire remaining cross-sectional area but instead will be redistributed in an uneven pattern that is highest at the edges of the hole as shown in the image. This phenomenon is known as stress concentration.
As long as there is enough mass (mast) around the hole the weight can be transferred around. If there is a flaw in the hole, then stresses get transferred differently. You want a nice smooth transition, either round or oval.
