Jim Miller wrote:
"What`s the "typical" tension necessary to keep a 88ft doublet aloft?"

Table 2 on page 20-3 of the 19th edition of the "ARRL Antenna Book"
recommends 8 pounds tension for #18AWG hard-drawn copper wire.

Many issues are involved in tensioning. For calculations see Ed Laport`s
"Radio Antenna Engineering" page 346.

Best regards, Richard Harrison, KB5WZI