Junk Mass 24/75 for Charge master 24/40-3

[gotwind]

I have a master volt battery charger, this is a Mass 24/75. This can only take 240v and has a max output of 75 amps. We are rarely in marinas and also now on the wrong side of the Atlantic for 240 volts.
We run mainly on solar but on occasions need to top up. We have a Honda 2000i (240 volt) however cannot use this to charge the batteries as the battery charger trips it out with to large a load.
My intention is to remove old battery charger and replace with a Charge Master 24/40-3. This can pull only 40 amps so should not trip out the Honda 2000i and can be plugged into 240 and 110 volt shore power. My small issue is that Master volt claim this is good up to a 400 amp hour bank. We are around 450 (at 24 volts) amp hours with ambitions to expand. Is the only disadvantage to under-sizing the battery charger to line up with the Honda a longer charge time or am I missing something.

Thanks