Problem with signs in dcolumn package

I want to create a table with multicolumns where numbers are vertically aligned at the decimal sign, so I used the dcolumn package. Some of my numbers have negative signs. For every second column my code perfectly works but not for the other columns. Can anybody figure out what I did wrong? Did I place the D{.}{.}{-1} commands at the right place? My \textwidth commands seem to look a bit complicated but the table I posted here is just a small part of a very big multicolumn table where I need to specify the width of each column in order to get it fit to one page.

\documentclass[11pt,a4paper,twoside]{article}

\usepackage{dcolumn}
\usepackage{booktabs}

\begin{document}


\begin{table}[!htp]

\label{tab:troistorrents_differences}
\begin{tabularx}{\textwidth}
{p{0.3\textwidth}
p{0.05\textwidth}D{.}{.}{-1}
p{0.05\textwidth}D{.}{.}{-1}
p{0.05\textwidth}D{.}{.}{-1}
p{0.05\textwidth}D{.}{.}{-1}
p{0.05\textwidth}D{.}{.}{-1}
p{0.05\textwidth}D{.}{.}{-1}
}

\addlinespace \toprule[0.5pt] \addlinespace

\multicolumn{1}{l}{\textbf{Position}}  &  \multicolumn{6}{c}{\textbf{Model1}}\\
& \multicolumn{2}{l}{82m Mast} & \multicolumn{2}{l}{SODAR 1}& \multicolumn{2}{l}{SODAR 2}  \\
& m/s & \% &  m/s & \% & m/s & \%   \\


\addlinespace \midrule \addlinespace

 Mast 1   & 0.0  & 0.0  & -0.3 & -7.4  & -0.3 & -8.4    \\
SODAR 1     & 0.4  & 7.8  & 0.0  & 0.0   & 0.1  & 1.3     \\
SODAR 2     & 0.3  & 7.8  & 0.0  & 0.0   & 0.0  & 0.0     \\
 Mast 2  & -0.1 & -2.5 & -0.4 & -10.8 & -0.5 &  -12.5   \\

\addlinespace \bottomrule[0.5pt] \addlinespace
\end{tabularx}
\end{table}

\end{document}