diff --git a/platformio_override.sample.ini b/platformio_override.sample.ini
index 6f86b248..9fbb345d 100644
--- a/platformio_override.sample.ini
+++ b/platformio_override.sample.ini
@@ -191,6 +191,22 @@ build_flags = ${common.build_flags} ${esp8266.build_flags}
 ;   -D HW_PIN_MISOSPI=9
 
 
+# ------------------------------------------------------------------------------
+# Optional: build flags for speed, instead of optimising for size.
+# Example of usage: see [env:esp32S3_PSRAM_HUB75]
+# ------------------------------------------------------------------------------
+
+[Speed_Flags]
+build_unflags = -Os ;; to disable standard optimization for small size
+build_flags =
+  -O2 ;; optimize for speed
+  -free -fipa-pta ;; very useful, too
+  ;;-fsingle-precision-constant ;; makes all floating point literals "float" (default is "double")
+  ;;-funsafe-math-optimizations ;; less dangerous than -ffast-math; still allows the compiler to exploit FMA and reciprocals (up to 10% faster on -S3)
+  # Important: we need to explicitly switch off some "-O2" optimizations
+  -fno-jump-tables -fno-tree-switch-conversion                 ;; needed - firmware may crash otherwise
+  -freorder-blocks -Wwrite-strings -fstrict-volatile-bitfields ;; needed - recommended by espressif
+
 
 # ------------------------------------------------------------------------------
 # PRE-CONFIGURED DEVELOPMENT BOARDS AND CONTROLLERS
@@ -564,10 +580,10 @@ build_flags = ${common.build_flags}
 
 [env:adafruit_matrixportal_esp32s3]
 ; ESP32-S3 processor, 8 MB flash, 2 MB of PSRAM, dedicated driver pins for HUB75
+board = adafruit_matrixportal_esp32s3
 ;; adafruit recommends to use arduino-esp32 2.0.14
 ;;platform = espressif32@ ~6.5.0
 ;;platform_packages = platformio/framework-arduinoespressif32 @ 3.20014.231204 ;; arduino-esp32 2.0.14
-board = adafruit_matrixportal_esp32s3
 platform = ${esp32s3.platform}
 platform_packages =
 upload_speed = 921600
@@ -587,21 +603,24 @@ build_flags = ${common.build_flags} ${esp32s3.build_flags} -D WLED_RELEASE_NAME=
 lib_deps = ${esp32s3.lib_deps}
   https://github.com/mrfaptastic/ESP32-HUB75-MatrixPanel-DMA.git#aa28e2a ;; S3_LCD_DIV_NUM fix
 
-board_build.partitions = tools/partitions-8MB_spiffs-tinyuf2.csv    ;; supports the adafruit UF2 bootloader (recommended!)
+board_build.partitions = ${esp32.large_partitions}                  ;; standard bootloader and 8MB Flash partitions
+;; board_build.partitions = tools/partitions-8MB_spiffs-tinyuf2.csv ;; supports adafruit UF2 bootloader
 board_build.f_flash = 80000000L
 board_build.flash_mode = qio
 monitor_filters = esp32_exception_decoder
 custom_usermods = audioreactive
 
 [env:esp32S3_PSRAM_HUB75]
-;; MOONHUB HUB75 adapter board
+;; MOONHUB HUB75 adapter board (lilygo T7-S3 with 16MB flash and PSRAM)
 board = lilygo-t7-s3
 platform = ${esp32s3.platform}
 platform_packages =
 upload_speed = 921600
 build_unflags = ${common.build_unflags}
+              ${Speed_Flags.build_unflags}    ;; optional: removes "-Os" so we can override with "-O2" in build_flags
 build_flags = ${common.build_flags} ${esp32s3.build_flags} -D WLED_RELEASE_NAME=\"esp32S3_16MB_PSRAM_HUB75\"
-              -DARDUINO_USB_CDC_ON_BOOT=1 -DARDUINO_USB_MODE=1      ;; for boards with USB-OTG connector only (USBCDC or "TinyUSB")
+              ${Speed_Flags.build_flags}      ;; optional: -O2 -> optimize for speed instead of size
+              -DARDUINO_USB_CDC_ON_BOOT=1 ;; -DARDUINO_USB_MODE=1      ;; for boards with USB-OTG connector only (USBCDC or "TinyUSB")
               -DBOARD_HAS_PSRAM
               -DLOLIN_WIFI_FIX ; seems to work much better with this
               -D WLED_WATCHDOG_TIMEOUT=0
@@ -615,7 +634,8 @@ build_flags = ${common.build_flags} ${esp32s3.build_flags} -D WLED_RELEASE_NAME=
 lib_deps = ${esp32s3.lib_deps}
            https://github.com/mrfaptastic/ESP32-HUB75-MatrixPanel-DMA.git#aa28e2a ;; S3_LCD_DIV_NUM fix
 
-board_build.partitions = ${esp32.default_partitions}
+;;board_build.partitions = ${esp32.large_partitions}               ;; for 8MB flash
+board_build.partitions = ${esp32.extreme_partitions}               ;; for 16MB flash
 board_build.f_flash = 80000000L
 board_build.flash_mode = qio
 monitor_filters = esp32_exception_decoder