Here are a couple of slim
tanks to consider. To be honest, I'm not sure if standard length Boge cartos will fit them. If not, the Cherry Vape universal drip tip is a good work around to use Boge cartos in XL length tanks. There are also Boge XXL cartos, which are longer and work well in tanks.
SmokTech 3.5ml Tanks
SmokTech 2.5ml eGo Tanks
As to the cracking issue, I couldn't say whether or not these tanks would hold up to your e-liquids. There are some tanks available with glass or stainless steel sleeves, but those can be rather pricey, compared to the cost of your kGo, but they won't crack due to tank-hostile e-liquids.