About finally sketch size...there are two options:

• arduino-esp32 git released before 05.03.2018
• current git + bigger app partition: http://desire.giesecke.tk/index.php/2018/01/30/change-partition-size/

Personally I use a second option to keep up with git changes.
BTW choose the partition size should be available in ide.

About sd loader...great idea! I didn't know this library, tnx for link!

Trust you're OK with me adding your code to my github page. : >

Thought the following might be of interest...

As i understand it, with the BLE client for Owon at present you need to use a version of arduino-esp32 git released prior to 04.03.2018. (guess that may change in future).

This wonderful creation linked below might address that i suspect - yes ?

Compile a version using the required version of git and burn it to an SD card for future re-use:
https://twitter.com/TobozoTagada/status/972845518966743040

Pretty awesome looking work there !! Thanks for putting the link up.

I loaded the code up but unfortunately I don't have an Owon to test it further..... Certainly tempted.....

Here is photo of it in action from Reaper7's github page: