Temperature will have an affect on your tank pressure.  It is possible to short yourself if there is not enough tank pressure but at 65-70 degrees you should be fine.  Hoses should be the same length to each knife to be uniform.  In the past we have not done that and have been fine but I would recommend doing it.  Not sure what system you are using for metering but we have used many and feel the raven system is by far the most accurate and easiest to troubleshoot.  Just my 2 cents