The log is available for debugging, and is not intended for data storage. It is not possible to adjust the size limit.
Are there any other options? The 'What you can build' page (http://developer.garmin.com/connect-iq/what-you-can-build/) speaks of a Local Storage API but provides no link to the documentation for it. Would I be able to setProperty a few thousand items perhaps? I'm sending Wind data over private ANT from a microcontroller and would like to store this at 1Hz frequency alongside the GPS/Power data from the Edge. Ideal solution would appear to be the custom data field FIT file, but as we're aware, this is still pending (is there any beta/test access to this programme perhaps?)
In the absence of writing to FIT file you might consider data compression. You could fit 5 x 6 bit readings into a word, which is a single storage entity. This allows storage of values up to 63 knots = 116 km/hr. This would reduce your storage requirements to 20kb by your example.
Another thing to consider other than sharkbait's idea ( hadn't considered that one!), might be to only save the average over the last 60 seconds, and do it once per minute instead of saving it at 1hz for testing. That will cut your data by 59/60ths and may make it easier to check out the data.
At the sizes you are describing, I can't think of any workarounds for you before the FIT data recording becomes available. The object store could be used, but it isn't designed to handle data of that size either and has a limit of ~8KB.
I think compressing your data for testing before the feature is released is your best bet.