Starizona is just about to release an F/4 focal reducer. It is a 2-inch format, with female 2-inch filter threads on the telescope side and male T-threads on the camera side. Price will be $279. To use it, you need a 2-inch visual back that has standard female SCT threads. For example, I've been using this one: https://agenaastro.c...-2-adapter.html
The Starizona F/4 focal reducer is designed for use with camera sensors up to 16mm diagonal or less, which means cameras like the ASI183 and smaller sensors. It will be possible to use it with a larger sensor like the 294 (23mm diagonal) and use region of interest (ROI) in SharpCap to crop the image down a bit and still get good results.
I've been doing some informal testing with a borrowed prototype with my classic (40-yr old) Celestron 8-inch SCT on an Evolution Alt-Az mount. Using my ASI385MC (which has a slightly larger sensor than the 224-based cameras), the results exceed the quality of what I am able to get with my "used" Meade 3.3 reducer. Stars are sharper (more pinpoint) with the Starizona F/4 reducer when used at its recommended spacing from the camera sensor. Even when used with 5mm more spacing than recommended to increase the focal reduction to F/3.9 (which is possible if using a smaller sensor), the edge of field curvature is no worse than with the Meade 3.3 reducer and stars are still sharper across the rest of the field than when using the Meade 3.3 reducer. While the Meade 3.3 reducer is only for 1/3-inch format sensors or smaller, the Starizona F/4 reducer will work well with sensors up to 16mm diagonal which makes it more versatile.
Here are some test images, all taken with my classic 8-inch SCT on an Evolution Alt-Az mount, with SharpCap live stacking and master dark. No filters used.
M81 22x15sec Meade 3.3 reducer @F/3.8