Looks like roughly 135 miles to the Trains from Jackman via Seboomook and Chesuncook lake.
From the Trains you're around 70-ish miles to Shin Pond Village via Libbys Camps.
IP to Jackman, then to Trains and SPV, Then head into County and stay in Ft Kent. Cross at Escourt Station? then head back towards Derby? That would be a great ride if you had 4-5 days to kill.
Back in the late 90s I went :
Day 1 Pittsburg to Greenville
Day 2 Greenville to Ashland
Day 3 Ashland, rode the north side of the County-stayed in Fort kent
Day 4 Ft. Kent thru Allagash - crossed at St Pamphile ( which you can no longer do) then continued on to Jackman via St Georges. Stayed at the Northland that night for $7 per person haha
Day 5 Jackman back to Pittsburg then drove home.
I believe that was around 1500 miles. Did it on my SRX700