If you put the tender on the battery when it's in the bike, do you run the risk of acid escaping with the outgasing?
I suppose it's a very slim possibility, esp if you have a poor quality battery. But I've been using BatteryTenders for years and years and have never had any problem with acid leakage or out gassing.
Trickle chargers should be less than 2amps. 1.5 would be best. You should be fine. As long as its a float charger, it should stop charging once the battery reaches full capacity. There are cheap brands that say they are float/automatic, but I wouldn't trust them. Besides, a quality charger is $35-$50 and should last you for decades. That averages $3 a year to maintain a battery.