OpenIntegrations/docs/en/examples/HTTPClient/SendPart.txt

    URL = "https://bin.openintegrations.dev";
    URL = URL + "/put";

    ChunkSize = 524288;
    Data      = GetBinaryDataFromString("Some data for sending");

    // Sending only "data for"
    StartPosition = 5;
    Bytes = 8;

    Result = OPI_HTTPRequests.NewRequest()
        .Initialize(URL)
        .SetBinaryBody(Data)
        .SendPart(StartPosition, Bytes) // <---
        .ReturnResponseAsJSONObject();