times number on beams crossing staves

[Maxime Brugidou]

Hello
i'm with the 2.6.3 version, i have 2 questions :
i wrote :
<<
\context Staff= "one" {
   \times 4/5 {\stemDown a'16[e' \change Staff=two \stemUp d'' c'']}
}
\context Staff= "two" {
   c'1
}
>>

it gave me the first pdf test1.pdf (should be me or my computer or my code)

and
\new PianoStaff <<
\context Staff= "one" {
   \times 4/5 {\stemDown a'16[e' \change Staff=two \stemUp d'' c'']}
}
\context Staff= "two" {
   c'1
}
>>

(more intersesting question i think) is it possible to move the number ? 
(the "5" is not at a very good place)
another one : in test2.pdf, the stave is cut. Is it because in my last 
ly file i used the \romoveEmptyStaff command ??

best regards

test1.pdf
Description: Adobe PDF document

test2.pdf
Description: Adobe PDF document