I would like to see a picture of the dome you designed. I haven’t used a dome yet, but I felt that a spherical plastic lid (like what would snap on a disposable paper cup) would do the job. The consensus seems to be conical for shedding snow. So many outdoor antennas are designed with flat tops, but pooling water must have a detrimental effect on those.
Regarding the Maxtenna, see:
Maxtenna is spoken of elsewhere in the forum as well. I thought I read somewhere that a helical antenna is a compromise. It trades omnidirectional reception for gain or something to that effect. Don’t quote me on that.