The good thing is you’re never more than 2 miles from the car park on the Pearce trail, and not only that, but there’s a number of old trails that are no longer signposted, plus the National XC course extension which turns left off the Hopton Park fireroad, follows the bottom bit of downhill, then climbs back up to the Pearce trail adding about 1/2 mile to the Titterhill climb…
You can also do the Bucknell Hill extension, though I tend to go left then right at the far end as the singletrack is much nicer than following the BOAT over the hill, and it ends up in the same place.
If you’re feeling really heinous you can go down the BOAT and Mynd road into Bucknell, go through the village, then ride up Bucknell Woods/Stowe Hill (preferably from the SE end), then go down the scary downhill with the big drop at the end, and back up Mynd Road to continue with the Bucknell Hill long loop.
If you’re still keen, there’s a few bits over at Black Hill but you’ll need an OS map!