Put the cowl, it really does affect the KE of this machine, it's like cutting the leading edge of your wing off. The fuse acts as a wing in KE so putting it on really will help.

Best thing to do is attach the cowl before making any CG changes or anything else. Then try it out again and then start making changes. Anything you change will be completely different once the cowl is on.

Also are the spats on, the extra drag of the wheels will pull it towards the belly too. SPats and swept undercarrigde will also do the trick.