I converted my 138S (same head as the 139) to a fan cooled 1000 watt point light source and I use the heat absorbing glass in mine. I have used the 300 watt Thorn lamp prior to conversion without the HA glass.

In the conversion to point light, the lamp envelope is about 1 1/2 inch from the HA glass. Without fan cooling I have melted the HA glass.

My filters are glass sandwiching acetate filters. I have not had problems with filters but I have cracked diffusion glass when I use it on long exposures. (Rarely)