RTSS and issues with DX6 (and older) games?

Windows 10 64-bit (16299.64)
GTX 1060 6 GB / Driver 388.31
MSI AB 4.4.0.11945 + RTSS 7.0.0.14877

I tried Rainbow Six (1998) and SWAT 3 (both GOG) but the overlay did not show up. I then switched to Medium detection level. This one worked but with major issues.

In rainbow six the frame rate was horrible and the game crashed in less than a minute and could not even reach the main menu. It was detected as DD (I suppose directdraw) by RTSS. I think it's a DX5 game?

In SWAT 3, the overlay would show up in some instances but not in others. It did not show up in mission. The frame rate in this game was also horrible and unplayable (seemed like single digits but I couldn't get the exact number since the overlay did not show up). It was also detected as DD. This game is DX6, IINM.
EDIT 3: It's the OSD that causes the frame rate drop in this game. Disabling it fixes the issue. No need to disable detection.

Am I doing something wrong? I don't have such issues with DX11, 9, 8 and OGL games. Haven't tried DX10. It seems the issue is with DX6 and older.

EDIT: I just installed Unreal Gold (GOG) and it works fine with RTSS. I chose the DX option in the game and set RTSS detection to Medium. The overlay shows up and the frame rate is at a fine 60 FPS. It is detected as DD. This game is also DX5?

EDIT 2: Tried No One Lives Forever and this one works fine too. It's a DX7 game. I suppose DX games older than DX8 are detected as DD, correct?
EDIT 4: Also tried the original Deus Ex, which is DX7 I think, and it has no issues, so it seems the problem is with DX6 and older.

 

I got exactly the same problem in Win7 x64 (nv driver 388.31) with Stalker CoP, where I am using older dx10 libraries in the bin folder, because dx11 sucks in this game (missing effects) and actual dx10 is randomly crashing after the platform KB update. So I had to enable Custom Support in RTSS, but then the game started with like 1fps, until I disabled RTSS completelly for this game, disabling OSD is not enough. I don't know what's going on, never got this problem with older RTSS versions, not even with 7.0.0 betas. Another game with this problem is vkQuake (Quake1 Vulkan port), but I admit that these are some obscure and old games. Nevertheless they didn't had any problems before...

EDIT: Its the frame limiter causing the problem, OSD is working.

EDIT2: Figured it out. I have the global limiter set as 5995 with denominator 100 (to get 59.95 for my monitor), but for Stalker it was set to 60 with no denominator in profile file. For some reason RTSS is using the global 100 denominator even for other profiles, where it isn't used, so it was limited to 0.6 fps... Maybe a bug or a feature, I don't know. Anyway after setting the Stalker profile as Limit=60 and LimitDenominator=1 its OK.

 

Your issue has nothing to do with mine then. I didn't enable the frame limiter for these games.

 

I'm new to this tool. My apologies. I gather that such issues with older DX games are normal then?

This is now off-topic but why DX7 games like No One Lives Forever are detected as DD though? Did the developers use directdraw instead of direct3d7 even with DX7, or this is how RTSS works?