Lots of hidden singletrack on Drummond hill – worth following your nose, as the summit ridge singletrack is a hoot.
Falls of Acharn on a bike is short n steep, but also leads onto some of the big estate tracks up back and over into Glen Almond.
South shore loch Tay – Glen Almond – back to Kenmore on Glen Quaich road is an ace ride on an bike, but is perfect on CX. Be aware two river crossings that get up quickly and huge.
Killin loop around glen Kendrum and Glen Dubh is a great few hours, and should be pretty snow free by March, make sure you finish back in Killin via Auchmore gorge singletrack.
Killin, South loch road to Ardeonaig and pick up path back to Killin over the Breachlaich dam road, and find the Auchmore singletrack descent (fab fun) is a nice couple of hours, and again hopefully snow free.
The col du Killin and Glen Lyon, Lawers Road loop is classic and really out there to say it is a road ride.
Rannoch area, black woods is well worth a visit, and can be linked with a great out and back from Glen Lyon over the Larig Ghalballich(sp.?) again a really out there middle of nowhere loop, and low enough to possibly be snow free.
Also look a heading 20 mins up A9 to do a big, big loop back to Rannoch via Loch Garry and back via Ericht and Alder bothy and Dalwhinnie/A9 side.
If you want a big hill silly, then just try up n over Sron a Clachain at Killin, or proper hill days on Munro sized hills are to be had on Schehallion, Ben A’Ghlo hills, Ben Vrackie and Ben Lawers.
Just echo above, you may get snow free, but likely not.