Add additional masks to BSgenome without BSgenomeForge

Question

[monovich]

Does anyone know if there is a way to add an additional mask to a BSgenome object loaded into memory without creating a new BSgenome package altogether? In my scenario I have a relatively small bed file of repeated sequences not masked by repeat masker or tandem repeat finder that I'd like to mask in my analysis, but I don't see any way to create a mask in the vignette beyond creating a new package which will be more effort than its worth for a single analysis.