Subtitles don't resize in full screen mode

[Gemma]

I am using bsplayer 2.67 (won't update because sbtitles adjustment in the newest versions is awful), with EVR video rendering.
When I switch to full screen subtitles size remains the same, even if I checked the "automatically rezize font and OSD" option.
Any hint?
It was working on my windows 7 laptop, on 8.1 not anymore.
Am I missing something?

[adicoto]

Go to preferences -> video -> rendering methodes and change from the drop-down box another one. Like overlay mixer or internal renderer.

[Gemma]

Tried them both. Nothing changes.
I have been able to have them resized for just a few seconds (don't ask me how) but then it went away again.
I'm really sick of this.
I've been using bsplayer for years now, but handling the subtitles is always complicated if not impossible.
Now they show on the black part of the screen (in full mode, on top and bottom) and NOT resized.
Please help. I tried all possible combinations and nothing seems to work.