Remix refuses to attach to Source SDK Base 2007

RTX Remix appears to refuse to attach itself to SDK Base 2007, a relatively old source build. Here's the d3d9 log output, since the program wasn't even able to boot.

[16:10:30.325] info:  Found default config for: Source Engine
[16:10:30.383] info:  Trying to open config file: d:\steamlibrary\steamapps\common\source sdk base 2007\bin\.trex\bridge.conf
[16:10:30.404] info:  Effective configuration:
[16:10:30.428] info:    sharedHeapSize = 2GB
[16:10:30.449] info:    useSharedHeap = True
[16:10:30.472] info:    cmdQueueSize = 3000
[16:10:30.494] info:    dataQueueSize = 3000
[16:10:30.517] info:    sharedHeapChunkSize = 4kB
[16:10:30.540] info:  Using shared heap for textures.
[16:10:30.562] info:  Using shared heap for static buffers.
[16:10:30.584] info:  Using shared heap for dynamic buffers.
[16:10:30.607] info:  ==================
[16:10:30.629] info:  NVIDIA RTX Remix Bridge Client
[16:10:30.651] info:  ==================
[16:10:30.674] info:  Version: remix-0.1.0
[16:10:30.697] info:  Loaded d3d9.dll from D:\SteamLibrary\steamapps\common\Source SDK Base 2007\hl2.exe
[16:10:30.721] warn:  Injected DirectInput8Create proc detected!
[16:10:30.772] info:  DirectInput8 hook attached.
[16:10:30.788] warn:  Injected DirectInputCreate proc detected!
[16:10:30.819] info:  DirectInput hook attached.
[16:10:30.843] info:  Initializing new shared memory object.
[16:10:30.898] info:  Shared memory: [ClientChannel_f134d85e-1191-48cb-96cb-4aeef6ef5991] created and initialized successfully!
[16:10:30.921] info:  Initializing new shared memory object.
[16:10:30.954] info:  Shared memory: [ServerChannel_f134d85e-1191-48cb-96cb-4aeef6ef5991] created and initialized successfully!
[16:10:30.977] info:  Initializing new shared memory object.
[16:10:31.000] info:  Shared memory: [SharedDataHeap_meta_f134d85e-1191-48cb-96cb-4aeef6ef5991] created and initialized successfully!
[16:10:31.023] info:  Initializing new shared memory object.
[16:10:31.163] info:  Shared memory: [SharedDataHeap_data_0_f134d85e-1191-48cb-96cb-4aeef6ef5991] created and initialized successfully!
[16:10:31.179] info:  Initializing new shared memory object.
[16:10:31.445] info:  Shared memory: [SharedDataHeap_data_1_f134d85e-1191-48cb-96cb-4aeef6ef5991] created and initialized successfully!
[16:10:31.491] info:  Initializing new shared memory object.
[16:10:31.832] info:  Shared memory: [SharedDataHeap_data_2_f134d85e-1191-48cb-96cb-4aeef6ef5991] created and initialized successfully!
[16:10:31.880] info:  Initializing new shared memory object.
[16:10:32.139] info:  Shared memory: [SharedDataHeap_data_3_f134d85e-1191-48cb-96cb-4aeef6ef5991] created and initialized successfully!
[16:10:32.181] err:   The shared memory map view could not be created (error code 8)!

Start by reproducing the attachment failure with Source SDK Base 2007 and review the D3D9 log through the shared-memory initialization. Focus on the reported error code 8 from the shared memory map view. Done means determining why boot fails and confirming successful attachment, or documenting that this SDK version is unsupported.