Method to rescale signals to mean length
If you really want to scale data, you can look at the scale transform, detailed in The scale representation, L. Cohen, 1993. There also exists a time-scaling method given in A. Papoulis, "Signal Analysis", McGraw-Hill, p. 290, 1977; one Matlab/Scilab/Octave implementation is provided in the DiscreteTFDs toolbox by  Jeffrey C. O'Neill.For the latter, you just have to provide a scaling factor proportional to the inverse of the signal's length.

However, in the same line as @Florian, and looking at the signals, I would be more prone to 1) find the maxima at fractional steps through interpolation (eg Quadratic Interpolation of Spectral Peaks) 2) realign with fractional filters (Splitting the unit delay: tools for fractional filter design) 3) truncate signals.