Have you considered APRS text messaging? Since the amount of data you are sending is short, and you are sending it to a specific other station in your use case, APRS text messaging uses a sequence number with acknowledgement and automatic retry if the ack isn't received.
You don't have to worry about channel jamming because your event can use a non-standard frequency for your APRS network. Every bicycle event I have worked has _never_ used the national APRS frequency for their support vehicle tracking.
Most desktop APRS applications can keep track of incoming APRS text messages, and the radios with built-in APRS support can (painfully) send text messages from their keypad.
So your Net Control station watching APRS position reports should be able to see texts from your field stations easily enough.
Just a suggestion.
author of YAAC ("Yet Another APRS Client"), which nicely supports monitoring text messages
-------- Original message --------
From: Mitch Winkle <ab4mw@...
Date: 9/12/21 08:35 (GMT-05:00)
Subject: Re: [draws and udrc] Peer to Peer "Chat" or Packet
Sourceforge project UIChat v 1.07 is a Linux (RPi) based AX.25 Bash
command line utility to send UI messages between stations with optional
Version 2.0 is now defunct, because the source code was lost and I don't
want to recreate it. :)
On 9/12/2021 08:15, Mitch Winkle wrote:
> You can read that in the specs. A bit much to explain on an email list.
> If you don't know what they are, it's probably not a solution for you.
> On 9/12/2021 08:13, Ed Bloom, KD9FRQ via groups.io
>> OK. Show what is a UI Frame?
>> How do I send such a thing via my Pi and DRAWS?
>> Do I need to install any new software?
>> Ed, KD9FRQ