ledger lines too thin

Windows 7, GIT commit: 9fd8764

1) create score
2) add a note on ledger line above or below staff
3) zoom in

Result: ledger line is only barely thicker than staff lines. Elaine Gould suggests making them twice as thick to make it easier to gauge how many ledger lines a note has, and this seems good advice.

Right now, default staff line thickness is 0.08sp, ledger line 0.12sp. Any objection to upping the default for ledger lines to 0.16sp? I tried setting this in a couple of scores and think it looks good, with no obvious downside (unlike a change in length).

Pointed out by Janek Warchol as a result of LilyP{ond engraving challenge, see http://engravingchallenges.freeforums.org/submission-3-musescore-2-0-de…