There ok, but a 12mm shaft is a bit small...id go for 17mm minimum..

im using these (RS Number 506-236) as i wanted something to take exstreme loading- for instance if NST hits it side on....verticles are weak to a good horizontal, with one hit on 360 i hit a verticle once, ruined his 10mm solid aluminium bulkheads and bent his 12mm thick hardox disc, bent the axle and smashed his disc motor...totaled his disc setup due to the weakness in his bulkheads....which apeared strong enough.

Because of this ive gone for a small diamater (less leverage to smash the bearings/bulkheads) a thick shaft (20mm solid stainless) and beefy bulkheads (20mm solid alumec) my bearings will be compressed up to the bulkheads, so the drum and bearings will be a perfect fit in the chassis....

If you plan on using that honey comb ali for your bulkheads id strongly reccomend otherwise.

Will and jamie seem to do well with HDPE bulkheads as they flex quite well.