If you HAVE to be the fastest, smallest, lightest build, the RIP120 from Rotorious FPV is what you are looking for. It is hard to explain but flying the RIP 120 feeds the 4s speed needs but you fly with the confidence that you would have from a TW! It's just not threatening enough to make you shaky on the stix. We are talking 97g AUW with 2s and 115g AUW with 3s and I just can't get over how much fun this little guy is! You will be trying things that you would never try on a 5" build and for that reason I see this being my freestyle trainer as well! Below are the links to the parts used and I really hope you get on board with this because I see it taking over the indoors racing in a big way. It just makes too much sense not to move in this direction if you have a good sized indoors facility at your disposal.
Frame: http://rotoriousfpv.com/product-category/frames/
FC:https://www.airbladeuav.com/collections/flight-controller/products/furious-piko-blx-micro-flight-controller-betaflight
ESC:https://www.airbladeuav.com/collections/electronic-speed-controllers/products/sunrise-cicada-busybee2-tiny-4-in-1-10a-blheli_s-esc
Motors:https://www.airbladeuav.com/collections/power-system-1/products/dys-be1104-7500kv-2s-brushless-racing-motors
Props:https://www.airbladeuav.com/collections/propellers/products/rotorx-rx3025-t-style-props-2cw-2ccw?variant=28500993987
AIO FPV:https://www.airbladeuav.com/collections/first-person-view-fpv-equipment/products/fx798t-5-8g-25mw-video-transmitter-600tvl-camera-combo?variant=23037222083
RX:https://www.amazon.com/Lemon-RX-DSM2-Satellite-Receiver/dp/B00SUM5GMW/ref=sr_1_4?ie=UTF8&qid=1484853243&sr=8-4&keywords=lemon+rx
